Symbols: Add GenericArguments to FSharpEntity

[auduchinok]

This is a continuation of #16456. It adds a public API for getting type arguments from resolved FSharpEntity items, so type arguments are accessible in cases like this:

int list
IList<int>
T<_>

The new API is not perfectly aligned with a similar one in FSharpSymbolUse, and I'm still thinking about ways to unify them. For now this seems to work good enough, and I'd like to make it available for use in the meanwhile.

[github-actions]

❗ Release notes required

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✅ Found changes and release notes in following paths:

Change path	Release notes path	Description
src/Compiler	docs/release-notes/.FSharp.Compiler.Service/8.0.300.md

[auduchinok]

This is ready.