[chore][pkg/ottl] Apply more standards to RemoveXML converter (#35463)

This PR just applies a couple more standards that I've been following
with the other XML converters. Namely:
- Create the function via the factory to ensure the constructor
validation is applied
- Use `xmlquery.QueryAll` instead of the deprecated `xmlquery.FindEach`

pkg/ottl/ottlfuncs/func_remove_xml.go

@@ -47,7 +47,13 @@ func removeXML[K any](target ottl.StringGetter[K], xPath string) ottl.ExprFunc[K
 		} else if doc, err = parseNodesXML(targetVal); err != nil {
 			return nil, err
 		}
-		xmlquery.FindEach(doc, xPath, func(_ int, n *xmlquery.Node) {
+
+		nodes, err := xmlquery.QueryAll(doc, xPath)
+		if err != nil {
+			return nil, err
+		}
+
+		for _, n := range nodes {
 			switch n.Type {
 			case xmlquery.ElementNode:
 				xmlquery.RemoveFromTree(n)
@@ -60,7 +66,7 @@ func removeXML[K any](target ottl.StringGetter[K], xPath string) ottl.ExprFunc[K
 			case xmlquery.CharDataNode:
 				xmlquery.RemoveFromTree(n)
 			}
-		})
+		}
 		return doc.OutputXML(false), nil
 	}
 }
@@ -82,7 +88,7 @@ func parseNodesXML(targetVal string) (*xmlquery.Node, error) {
 	if err != nil {
 		return nil, fmt.Errorf("parse xml: %w", err)
 	}
-	if !preserveDeclearation {
+	if !preserveDeclearation && top.FirstChild != nil {
 		xmlquery.RemoveFromTree(top.FirstChild)
 	}
 	return top, nil

pkg/ottl/ottlfuncs/func_remove_xml_test.go

@@ -91,15 +91,28 @@ func Test_RemoveXML(t *testing.T) {
 			xPath:    "//text()['*delete*']",
 			want:     `<?xml version="1.0" encoding="UTF-8"?><a></a>`,
 		},
+		{
+			name:     "ignore empty",
+			document: ``,
+			xPath:    "/",
+			want:     ``,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			target := ottl.StandardStringGetter[any]{
-				Getter: func(_ context.Context, _ any) (any, error) {
-					return tt.document, nil
-				},
-			}
-			exprFunc := removeXML(target, tt.xPath)
+			factory := NewRemoveXMLFactory[any]()
+			exprFunc, err := factory.CreateFunction(
+				ottl.FunctionContext{},
+				&RemoveXMLArguments[any]{
+					Target: ottl.StandardStringGetter[any]{
+						Getter: func(_ context.Context, _ any) (any, error) {
+							return tt.document, nil
+						},
+					},
+					XPath: tt.xPath,
+				})
+			assert.NoError(t, err)
+
 			result, err := exprFunc(context.Background(), nil)
 			assert.NoError(t, err)
 			assert.Equal(t, tt.want, result)