Remove unnecessary calls to GetTypeInfo

[eerhardt]

GetTypeInfo() calls are no longer necessary just to use Reflection APIs. And typically they allocate a small TypeDelegator object when used, so they should be avoided when not necessary.

I removed the obvious cases from the product, and a few occurrences in test code. However, I didn't tackle every place test code was calling it as there is a diminishing return.

Similar work is done in dotnet/runtime:

• Remove some unnecessary GetTypeInfo usage runtime#44414
• Remove unnecessary GetTypeInfo from Microsoft.Extensions. runtime#44891

[eerhardt]

Note these changes match what was done in dotnet/runtimes ActivatorUtilities. See https://github.com/dotnet/runtime/pull/40227/files#diff-d04fd33a5eba20dc5b742e17b751d3b9c0860d114b73c777a0e140c1ceaccf6fR57

[davidfowl]

Hmmmm when?

[halter73]

Is constructor.IsPublic implied? Or does this change ActivatorUtilities.CreateInstance to use non-public ctors? If it's the latter, this seems like a fairly major breaking change.

[BrennanConroy]

Previous conversation about this: https://github.com/dotnet/runtime/pull/40227/files#r463897549
TLDR: GetConstructors returns only public constructors

[eerhardt]

Just looked again, it also only returns Instance constructors, so we could remove the IsStatic check from both copies (runtime and aspnetcore) of this code.

https://github.com/dotnet/runtime/blob/1821d9c14b970d58e0768256de138b6c0287e07d/src/libraries/System.Private.CoreLib/src/System/Type.cs#L175-L178

[Pilchie]

Throwing a bunch of areas on for people to take a look.

[Tratcher]

/azp run

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