Tie language features to the langver flag

Properly implement type inference for C# member access expressions.

Only compute entry points when compiling everything.

Don't invoke SignFiles if there's no files to sign

Fixes #12113

This silences a build warning.

Merge future-stabilization into master

* Test ExportedType table content

* Refactoring of code emitting exported types

* Remove MetadataWriter.GetExportedTypeFlags

Merge pull request #12083 from jasonmalinowski/tweaks-while-investigating-duplicate-project-references

Tweaks while investigating duplicate project references

	Make more deletion code non-VB specific.

Remove VB specialization.

Fixing the VsixVersion to be 42.42.42.42 for unofficial builds.

Ignore VS Code-generated dirs in gitignore

Bump package versions to beta4

Added initial support for explicit tuple conversions