Merge NullableAnnotation.NotApplicable and Disabled to None, and rename NullableFlowState.NotApplicable to None for consistency.

Fixes #37310
Fixes #37279

Update the stub API to remove Nullability and replace with NullableAnnotation and NullableFlowState, and update the
the rewriter to use that instead of the Nullability enum.

This change removes the following APIs:
- TypeSymbol.BaseType
- TypeSymbol.Interfaces
- TypeSymbol.AllInterfaces
- NamedTypeSymbol.TypeArguments
- TypeParameterSymbol.ConstraintTypes

These APIs simply delegate the work to APIs with "NoUseSiteDiagnostics" suffix and are not supposed to be used inside compilers. They were left in the code-base because they used to be part of the public surface and the names were nicer, but they are no longer part of the public surface.

* Call this.DeclaringCompilation.EnsureReadOnlyAttributeExists() when needed

* Promote EmbeddedAttribute to be used by both compilers

* Generate Embedded attributes on PE Module Builder

* Thread PEModuleBuilder through Symbol.AddSynthesizedAttributes()

* Fix failing tests

* Base case passing

* Refactor ReadOnlyAttribute to IsReadOnlyAttribute

* Fix build break

* More Tests

* Clean up

* PR Comments #1

PR Comments #3

PR Comments #4

PR Comments #5

PR Comments #6

PR Comments # 7

* Handle NoPIA

Added more tests

* Lambdas and Local functions no longer generate attributes in symbols

Added tests for constructors and operators

Signal need for synthesized attributes in local rewriter for lambdas an local functions

Clean up

* Clean up

* More PR Feedback

* Adding more tests

* More PR Comments

* More tests for explicit interface implementations

* Latest PR Comments

* Moved EnsureIsReadOnlyAttributeExists to AfterAddingTypeMembersChecks

* Fix failing tests

Fixes:https://github.com/dotnet/roslyn/issues/14334

Fixes #7659.

- Substitute underlying type with corresponding tuple type at the point of type reference.
- Adjusted implementation of symbol display to account for presence of names in the extension tuples.
- Implemented proper retargeting for tuple types (multi-targeting support).

Fixes #4163.

This is the initial run of the code formatter on the VB compiler source code.  Further runs I'll expand on this to include all VB code in a future run.

In some parts of our codebase, we use "verbatim crefs" where the compiler just passes the cref name out to the XML file and doesn't do any analysis of it. While there are some legitimate uses of these, there were many abuses in our source code. Worst of all, in some cases we had verbatim crefs on public types that referenced types that had since been renamed, or the syntax was wrong, etc. With this change, there's now an analyzer that issues a warning for all uses of them. In the places that are fair uses of them, the warning is suppressed. Going forward, adding suppressions should be considered fine as long as:

1) it's a reference to something in another layer or language
2) it's some framework type that's clearly never going to change ever

Otherwise, a proper, verifiable syntax should be used. Again, this isn't to say that verbatim crefs are universally bad, but just that we've proven we make mistakes with them and some guards should be put in place. (changeset 1360175)

Splits Microsoft.CodeAnalysis, Microsoft.CodeAnalysis.CSharp and Microsoft.CodeAnalysis.VisualBasic into portable and desktop assemblies.

Existing Core\Source, CSharp\Source and VisualBasic\Source directories are renamed to Core\Portable, CSharp\Portable and VisualBasic\Portable.
New sibling Desktop folders are added and non-portable source is moved there.
"System.Runtime" references has to be removed in order for the portable project system magic to automatically add facade references.
 (changeset 1281686)