Add span-based CopyTo and CopyToAsync methods (dotnet/coreclr#27639)

Add span-based CopyTo and CopyToAsync methods (dotnet/coreclr#27639)

* Add span-based CopyTo and CopyToAsync methods

* Update according to feedback

* Add span-based CopyTo overrides for MemoryStream

* Improve span-based CopyTo arguments validation

To avoid code duplication

* Update according to second review

Stream API is changed

* Resolve InternalReadSpan/Memory inlining

* Refactor ValidateCopyToArgs

* Update according to third review

* Update after fourth review

* Override span CopyTo for UnmanagedMemoryStream

* Apply suggestions from code review

Co-Authored-By: Stephen Toub <stoub@microsoft.com>
* Update after fifth review

* Add cross sync/async support for span-based CopyTo

* Call sync action directly in async context

* Rework cross sync/async support for span-based CopyTo

Co-Authored-By: Stephen Toub <stoub@microsoft.com>
Commit migrated from https://github.com/dotnet/coreclr/commit/6abc099d4a798dc9a267d04bc025efbcbf148473