Fixes #29291

* Reporting errors on foreach ref/readonly declarations in async/iterator methods

* PR Comments

Merged on behalf of @svick Thanks!

* Inaccessible extension methods should not be considered eligible candidates.
Fixes #25813

* __arglist cannot have an argument passed by 'in' or 'out'

* Fix build break

* PR Comments

* Previous PR comments

* Missing tests from test plan

* Enable unmanaged constraint on local functions

* Clean up

* PR Comments

* More tests

* PR Comments

Also block tuple binop in expression tree

Return FormattableString for BoundTupleExpression.Display/BoundStackAllocArrayCreation.Display and allow FormattableString in DiagnosticInfo.Arguments.

This includes tests for

- Language version checks for ref in for & foreach
- Additional tests around unary plus and ref assignment expressions
- Tests for ?., IDisposable, and ref assignment expressions
- Additional semantic model tests
- Additional IOperation tests

These are the blocking issues identified for the test plan https://github.com/dotnet/roslyn/issues/22466

- Update pe writer to not rely on updated System.Reflection.Metadata for arm64 support
  - Instead of using System.Reflection.Metadata support, write the PE as x64, and then
    modify it to have the correct machine.
- Add support for determistic PE generation with Arm64 platform
  - ensure that the hash used for timedatestamp is based on the contents with the Arm64 pe flag set
- Update resources to describe arm64 as a viable platform switch

* Source changes for unmanaged (PROTOTYPE for metadata)

* Modreqs for unmanaged as well

* Finished roundtripping metadata

* Added more tests

* Fix CI

* More tests

* Clean up