Generalize dynamic static-only restriction to include field initializers (was just ctor initializers)

Ensure that we generated a CompilationCompletedEvent for compilations with no source files (example an empty VSIX projects).

Move lines appearing in PublicAPI.Unshipped.txt files to
PublicAPI.Shipped.txt files and re-sort the latter.

Note: VB scripting APIs and APIs for IOperation continue to remain
unshipped.

This reverts commit 92ff3f8d.

Make compiler produce the same Product Build, Major, Minor and Private Parts in VersionInfo as VS2013 compiler when Assembly ProductAssemblyFileVersionAttribute and AssemblyInformationalVersion contain invalid format. Also introduce warning diagnostic for AssemblyInformationalVersion with invalid version string

Fixes #9759

Ports the compiler generator tools (syntax generator, bound tree
generator, et al.) to .NET core and runs the exes on CoreCLR instead of
the desktop framework.

Fixes #7136

This reverts commit b03e8478.

Makes the symbol lookup return no symbols when completing `base.` inside
of a REPL.

- avoid instantiating nullable type when doing operator overloading on enums
- avoid instantiating generics when checking for impossibly rare case of duplicated interface implementations
- skipping materializing of sequence point array

Include HasValue check in BoundSwitchStatement so any display class allocation is moved outside of the check

The flag name is "IOperation". Register opeartion actions and calling
SemanticModel.GetOperation while the feature is disabled will throw an
InvalidOperationException. Also log a non-fatal-watson when
SemanticModel.GetOperation crashes.