Fixes https://devdiv.visualstudio.com/DevDiv/_workitems?id=217718.

Provide an API to get unreferenced assembly identities obects from the diagnostics reported about them.

Use tuple syntax in the compiler

Support setting if an anonymous type's properties are mutable or not.

* CommonPEModuleBuilder refactoring

* Renames

* Use CommonPEModuleBuilder instead of IModule

* Remove IModule

* Move GetFiles to module builder

* Remove IAssembly

* Add comments, PR feedback

* Resolve merge conflicts

* Implement source link feature

* Fix CommonCompiler to open source link stream, add E2E tests

* Reduce code duplication across VB and C#

Revert "Revert "Revert "Revert "*DON'T MERGE INTO MASTER* Hide IOperation API behind a feature flag""""

This reverts commit d4d502e4.

This reverts commit c6a1c2c8.

* Tests: fix minasync Task<T> to derive from Task

* Tests: provide MinAsyncCorlibRef

This combines the async features of minasync with mincorlib to produce
a minimum unversioned corlib with async stubs.

* Compilation: use System.Object from target corlib

When creating a script compilation without an explicit return type,
System.Object was being resolved via reflection from the host.

This resulted in an implicit dependency of a script compilation on the
host corlib, even if a different corlib was specified as a reference
for the compilation (e.g. Xamarin.iOS).

Fix this by using System.Object as defined in the corlib resovled
for the compilation.

* Tests: fix minasync Task<T> to derive from Task

* Tests: provide MinAsyncCorlibRef

This combines the async features of minasync with mincorlib to produce
a minimum unversioned corlib with async stubs.

* Compilation: use System.Object from target corlib

When creating a script compilation without an explicit return type,
System.Object was being resolved via reflection from the host.

This resulted in an implicit dependency of a script compilation on the
host corlib, even if a different corlib was specified as a reference
for the compilation (e.g. Xamarin.iOS).

Fix this by using System.Object as defined in the corlib resovled
for the compilation.

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

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

This reverts commit a96d7825.

This reverts commit 92ff3f8d.