improve tests by using StackTrace API and diagnostic verifier

Add a code refactoring to convert if to switch

Make Local Functions follow brace newline option for methods

Add test binding redirect for System.Xml.XmlDocument

Add a code refactoring to convert numeric literals

Merge master into post-dev15

Show the lightbulb when there are available refactorings at the current location.

Tweak completion filtering behavior. #2

Show object creation completion before braces

Fix race conditions caused by doing something *after* the corresponding symbol completion bit was set. (#16740)

* Fix race conditions caused by doing something *after* the corresponding symbol completion bit was set.
Fixes #16706

Show `base` keyword within expression-bodied accessors

lower server stream buffer size.

Arrow-expression-bodies should auto-collapse when 'collapse to definitions' is invoked.

Add missed code style options to automation object

* allow use of a byref parameter inside of nameof

* remove random whitespace changes

* add handling for linq queries

* And -> AndAlso

* change name of linq query

* add linq assembly ref

Adrian was reporting high LOH fragmentation in OOP process due to this. I did some experiment and lowered buffer size to 12K that seems keeping current synch perf similar to now but way lower buffer size.