Revert change to a CompletionItem property which pythia depends on

Also add required helpers so we can remove the dependency

src/EditorFeatures/Core/Implementation/IntelliSense/AsyncCompletion/CompletionSource.cs

@@ -558,7 +558,7 @@ private VSCompletionItem Convert(
                 // roslynItem generated by providers can contain an insertionText in a property bag.
                 // We will not use it but other providers may need it.
                 // We actually will calculate the insertion text once again when called TryCommit.
-                if (!roslynItem.Properties.TryGetValue(CommonCompletionItem.InsertionTextProperty, out var insertionText))
+                if (!SymbolCompletionItem.TryGetInsertionText(roslynItem, out var insertionText))
                 {
                     insertionText = roslynItem.DisplayText;
                 }

src/EditorFeatures/Core/Implementation/LanguageServer/Handlers/Completion/CompletionHandler.cs

@@ -260,9 +260,7 @@ static async Task<TCompletionItem> CreateCompletionItemAsync<TCompletionItem>(
                 // If the feature flag is off, return an InsertText.
                 else
                 {
-                    completionItem.InsertText = item.Properties.ContainsKey(CommonCompletionItem.InsertionTextProperty)
-                        ? item.Properties[CommonCompletionItem.InsertionTextProperty]
-                        : completeDisplayText;
+                    completionItem.InsertText = SymbolCompletionItem.TryGetInsertionText(item, out var insertionText) ? insertionText : completeDisplayText;
                 }
 
                 var commitCharacters = GetCommitCharacters(item, commitCharacterRulesCache, supportsVSExtensions);

src/Features/CSharp/Portable/Completion/CompletionProviders/CrefCompletionProvider.cs

@@ -419,7 +419,7 @@ private static CompletionItemRules GetRules(string displayText)
 
         protected override Task<TextChange?> GetTextChangeAsync(CompletionItem selectedItem, char? ch, CancellationToken cancellationToken)
         {
-            if (!selectedItem.Properties.TryGetValue(CommonCompletionItem.InsertionTextProperty, out var insertionText))
+            if (!SymbolCompletionItem.TryGetInsertionText(selectedItem, out var insertionText))
             {
                 insertionText = selectedItem.DisplayText;
             }

src/Features/Core/Portable/Completion/CommonCompletionItem.cs

@@ -12,7 +12,6 @@ namespace Microsoft.CodeAnalysis.Completion
     internal static class CommonCompletionItem
     {
         public const string DescriptionProperty = nameof(DescriptionProperty);
-        public const string InsertionTextProperty = nameof(InsertionTextProperty);
 
         public static CompletionItem Create(
             string displayText,

src/Features/Core/Portable/Completion/Providers/SymbolCompletionItem.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -17,6 +18,8 @@ namespace Microsoft.CodeAnalysis.Completion.Providers
 {
     internal static partial class SymbolCompletionItem
     {
+        private const string InsertionTextProperty = "InsertionText";
+
         private static readonly Func<IReadOnlyList<ISymbol>, CompletionItem, CompletionItem> s_addSymbolEncoding = AddSymbolEncoding;
         private static readonly Func<IReadOnlyList<ISymbol>, CompletionItem, CompletionItem> s_addSymbolInfo = AddSymbolInfo;
         private static readonly char[] s_projectSeperators = new[] { ';' };
@@ -43,7 +46,7 @@ private static CompletionItem CreateWorker(
 
             if (insertionText != null)
             {
-                props = props.Add(CommonCompletionItem.InsertionTextProperty, insertionText);
+                props = props.Add(InsertionTextProperty, insertionText);
             }
 
             props = props.Add("ContextPosition", contextPosition.ToString());
@@ -254,7 +257,10 @@ public static int GetDescriptionPosition(CompletionItem item)
             => GetContextPosition(item);
 
         public static string GetInsertionText(CompletionItem item)
-            => item.Properties[CommonCompletionItem.InsertionTextProperty];
+            => item.Properties[InsertionTextProperty];
+
+        public static bool TryGetInsertionText(CompletionItem item, [NotNullWhen(true)] out string? insertionText)
+            => item.Properties.TryGetValue(InsertionTextProperty, out insertionText);
 
         // COMPAT OVERLOAD: This is used by IntelliCode.
         public static CompletionItem CreateWithSymbolId(

src/Features/Core/Portable/ExternalAccess/Pythia/Api/PythiaCompletionProviderBase.cs

@@ -4,12 +4,12 @@
 
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.Completion;
 using Microsoft.CodeAnalysis.Completion.Providers;
 using Microsoft.CodeAnalysis.LanguageServices;
-using Microsoft.CodeAnalysis.Options;
 using Microsoft.CodeAnalysis.Shared.Utilities;
 
 namespace Microsoft.CodeAnalysis.ExternalAccess.Pythia.Api
@@ -48,11 +48,16 @@ public static ImmutableArray<SymbolDisplayPart> CreateRecommendedKeywordDisplayP
             => RecommendedKeyword.CreateDisplayParts(keyword, toolTip);
 
         public static Task<CompletionDescription> GetDescriptionAsync(CompletionItem item, Document document, SymbolDescriptionOptions displayOptions, CancellationToken cancellationToken)
-            => SymbolCompletionItem.GetDescriptionAsync(item, document, displayOptions, cancellationToken);
+            => SymbolCompletionItem.HasSymbols(item)
+            ? SymbolCompletionItem.GetDescriptionAsync(item, document, displayOptions, cancellationToken)
+            : Task.FromResult(CommonCompletionItem.GetDescription(item));
 
         public static CompletionDescription GetDescription(CompletionItem item)
             => CommonCompletionItem.GetDescription(item);
 
+        public static bool TryGetInsertionText(CompletionItem item, [NotNullWhen(true)] out string? insertionText)
+            => SymbolCompletionItem.TryGetInsertionText(item, out insertionText);
+
         public override Task<CompletionChange> GetChangeAsync(Document document, CompletionItem item, char? commitKey = null, CancellationToken cancellationToken = default)
             => base.GetChangeAsync(document, item, commitKey, cancellationToken);