[ask mode]Remove unwanted public APIs and enable public API analyzers for Interactive (Editor) Features

Implements recursive reference aliases

Public API changes recommended by the design team for the new Analyzer/Suppression APIs.
• CompilationWithAnalyzerOptions should be sealed
• CompilationWithAnalyzerOptions.AnalyzerOptions should be renamed Options
• SuppressionInfo should be sealed
• AnalyzerTelemetry API changes as per this comment.

There are no functionality changes here.

Fixes #6044

Propagate imports to synthesized methods

Fixes #2501

- CompilationWithAnalyzerOptions should be sealed
- CompilationWithAnalyzerOptions.AnalyzerOptions should be renamed Options
- SuppressionInfo should be sealed
- AnalyzerTelemetry API changes as per [this](https://github.com/dotnet/roslyn/issues/5974#issuecomment-149987997) comment.

There are no functionality changes here.

Fixes #6044

provide HelpKeyword information for offline help

Address the performance issues for bulk suppression in IDE.

1. "Suppress active issues" command from solution explorer was doing couple of builds - one command line build to compute the FxCop diagnostics and another intellisense build to fetch Roslyn diagnostics. This change removes the second build and instead uses the diagnostics emitted from the build for suppression.

2. Bulk suppressing multiple diagnostics from error list/suppress active issues command was spending more than 50% of time in formatting the generated global suppressions file. This delay grows significantly larger with 1000+ issues being suppressed. This fix changes us to not format the entire suppressions file at once, but instead format each attribute separately and avoid formatting the batched file. This significantly brings down the formatting time.

3. Thread in the cancellation token during batch fix computation - otherwise cancelling the wait dialog while computing suppressions fix will make VS unresponsive.

Fixes #6066

1. "Suppress active issues" command from solution explorer was doing couple of builds - one command line build to compute the FxCop diagnostics and another intellisense build to fetch Roslyn diagnostics. This change removes the second build and instead uses the diagnostics emitted from the build for suppression.

2. Bulk suppressing multiple diagnostics from error list/suppress active issues command was spending more than 50% of time in formatting the generated global suppressions file. This delay grows significantly larger with 1000+ issues being suppressed. This fix changes us to not format the entire suppressions file at once, but instead format each attribute separately and avoid formatting the batched file. This significantly brings down the formatting time.

3. Thread in the cancellation token during batch fix computation - otherwise cancelling the wait dialog while computing suppressions fix will make VS unresponsive.

Fixes #6066

Set State.WaitingForInput in PrepareForInput [stabilization]

Do async locking correctly

Fixes REPL initialization and SourcePaths handling

Don't call PumpingWaitResult for the result of GetSyntaxTreeAsync

Fix a race condition in AsyncQueue.EnqueueCore

Fix generate end construct when invoked on an accessor

This change increases the severity of analyzer exception diagnostic

Cause: We are seeing intermittent deadlocks during build on linux machines running our test suites. The deadlock happens when one thread invokes AtomicSetFlagAndRaiseSymbolDeclaredEvent, and succeeds in setting the flag and invokes SymbolDeclaredEvent while holding onto the lock. The task scheduler decides to inline the event processing, which attempts to execute analyzers while holding onto the _diagnosticLock. Another thread meanwhile is already executing analyzers and calls back into the compiler and is waiting on _diagnosticLock.

Fix: Fix the AsyncQueue.EnqueueCore method to invoke SetResult on the waiter task completion source on a separate task. This ensures that no external code executes while attempting to Enqueue a compilation event, and hence cannot deadlock.

Testing: All tests pass locally.

Fixes #https://github.com/dotnet/roslyn/issues/6098

[AskMode] VisualBasicUnboundIdentifierDiagnosticAnalyzer fix
Fixes #5920

[ask mode] Rename WithCompilationScriptInfo -> WithScriptCompilationInfo

Test `EmitSequenceOfBinaryExpressions_03` in VB is failing in signed builds.

[ask mode] Fixes crash in InteractiveEvaluator when the CWD changes

Use the same .rsp file for VS REPL as we use for csi.exe

We guarantee the tasks returned from GetSyntaxTreeAsync() are always
safe to wait for on any thread directly, so this was never necessary.

[AskMode] Change parsing of #! from Comment -> Directive...

(fixes #6308)

Do not crash on lexically bad floating-point tokens

Make dump directory predictable

This makes the emit dump directory predictable so it can be archived in Jenkins for investigation.

Remove restore from targets file

This change increases the severity of analyzer exception diagnostic (AD0001), generated when an analyzer throws an exception, from info to a warning. Additionally, its descriptor is now reported as a supported diagnostic descriptor of the compiler analyzer, which ensures that it shows up in the ruleset editor.

Fixes #3707

Our current setup has restore as a distinct step from build (done before).  Removing this code which used to attempt to restore in the middle of build.  At this point it's just chewing up build cycles.

Test EmitSeuqnceOfBinaryExpressions_03 is failing the stabilization and master
signed builds. Tracked by bug #6077