net7 cleanup and fix broken pinned/unmanaged flag detection (#74)

* merge

* add validation for Delegates usage in AOT mode; make support detectable

* RuntimeFeature.IsDynamicCodeSupported: actually 3.0

* Update tests/AotTests/AotTests.csproj

Co-authored-by: Eric Erhardt <eric.erhardt@microsoft.com>

* Update tests/AotTests/AotTests.csproj

Co-authored-by: Eric Erhardt <eric.erhardt@microsoft.com>

* nits

* first pass at removing T : unmanaged constraints

* finish removing MakeGeneric*

* nulls and other nits

* allow MemoryMarshal.CreateSpan in NS2.1

* fix long DEBUG delay on dueling threads test

* and sync

---------

Co-authored-by: Eric Erhardt <eric.erhardt@microsoft.com>

move to main

rev refs

improve detection of faulty bindings

release notes

release notes; package updates

version for docs

2.1 release

release notes for 2.0.25

release notes 2.0.22