[release/6.0] Treat 'abstract' properties the same as 'virtual' for src-gen#59771

danmoseley merged 2 commits intorelease/6.0dotnet/runtime:release/6.0from

backport/pr-59707-to-release/6.0dotnet/runtime:backport/pr-59707-to-release/6.0Copy head branch name to clipboard