Fixed code styles and added one more test.

tests for AddUsing in Conditional Access Expression cases.

SyntaxFacts.GetExpressionOfMemberAccessExpression was looking for
patterns that could be ConditionalAccessExpression. It was looking only
two levels up from the current node. We hit a case where the
ConditionalAccessExpression was four levels higher. So, in general,
instead of dealing with various cases, we should use the
GetParentCondtionalAccessExpression helper that walks up from a given
node and finds a ConditionalAccessExpression if one exists in a parent
hierarchy. This change is C# only. The VB implementation of this method
correctly uses GetCorrespondingConditionalAccessExpression in this case.

Fix codegen for integral switches with only null and default cases.

Get document moniker from IVsProject instead of RDT

Update System.Reflection.Metadata to -0014

Add exception filters to get better crash dump for exceptions during conflict resolution

We were forgetting to emit a branch to the fallthrough case.
Normally emitting the jump table would do it, but in a case where the only nondefault label is the null label, no jump table is emitted.

Fixes #4701

Pay attention to sizes and lower bounds specified for multi-dimensional arrays in metadata signatures.

Add CscCore to CrossPlatform.sln

Make NuGet sources more deterministic

Async loading with property pages

If we failed to get a document moniker for the contained document, fail
now.  Otherwise we'd crash when attempting to create a document key.

Switching to IVsProject.GetMkDocument to get document moniker instead of
iterating through all the entries in the running object table. Also
cleaning up a bit of code while I'm here - It looks like we don't need
to determine Shared Hierarchy & Shared ItemId here anymore. It was there
for error list and it looks like with PR #2399 error list switched to a
different implementation.

Updates the mono toolset to mono built from source at tag
mono-4.2.0.207.

Updates the mono toolset to mono built from source at tag 4.2.0-207.

This is needed to unblock the core change to fix issue #4183.

project.json Fixes

Added a clear entry to our package sources to ensure builds on developer machines weren't inadvertently affected by local settings.

Pay attention to sizes and lower bounds specified for multi-dimensional arrays in metadata signatures.

Fixes #4954.

We will treat Sizes and LowerBounds similar to custom modifiers. They should match for the purpose
of signature comparison (overriding/implementing, etc), but shouldn't affect conversions.

Update the project.lock.json for FakeSign and upload a new nuget zip

#load directives...

It isn't needed, as the Workspace will notice changes in the Compilation
due to #loads.

Tidy up nuget artifacts for ResultProviders...

Fixes a subtle bug in branch optimizer.

Making stack scheduling optimizations more robust and fixing #4828

Performance improvements for the v2 analyzer driver

Using correct case in-sensitive comparer
Fixes #4782

Address PR feedback