Merge dev16.0-preview2 to master

This reverts commit 166349c8.

Merge dev16.0.x to dev16.0-preview2

Add tests to demonstrate that they are associative and commutative.
Add (skipped) tests to demonstrate that we have inconsistent meet and join functions.
    We will have to decide how to handle the differences.
I have not yet extracted the NullableState operations from ConversionsBase
    (e.g. testing if one NullableState is higher or lower than another in the lattice)
Also removed some inoperative code in MethodTypeInference

Merge dev16.0-preview2 to master

Implement Sync namespace and folder refactoring

Merge dev16.0-preview2 to master

Also replaces some unsafe code with Span<T>.

output paths are not specifically affecting semantics of code but some analyzer such as source based test discovery requires it to generate correct data. so they want to be re-analyzed when those are changed as well.

since output path are rarely get changed. decide to add it as one of cause to reanalyze projects.

Merge dev16.0-preview2 to master

Add a new SuppressMessageAttribute target scope to suppress diagnosti…

Merge dev16.0-preview2 to master

Merge dev16.0-preview2 to master

Smart indent when users type '{' even if 'format on typing' is off.

Delete a bunch of unused versions from FixedPackages.props

Merge dev16.0.x to dev16.0-preview2

Merge features/razor-far to 16.0 Preview 1 ( i cann't figure out how to rekick license/cla ) 

Merge pull request #31125 from jasonmalinowski/fix-metadata-reference-conversion-to-languages-without-compilations

Block conversion of references to F# projects from C# projects

Fixes #30561