* Classify C# 8 ControlKeywords

* Add unit test for C#8 control keyword classification

* Add Static Symbols classification
* Add Namespace name classification
* Add Label name classification
* Add Overloaded Operator classification
* Add Control Keyword classification
* Updated TaggedText to work with the new classifications
* Add common AbstractNameSyntaxClassifier class for sharing code

* Classify malformed XML Doc comments as XmlDocCommentText

* Added test for malformed xml doc comment classification

* Previous PR comments

* Missing tests from test plan

* Enable unmanaged constraint on local functions

* Clean up

* PR Comments

* More tests

* PR Comments

* Rename Foo to Goo

* Rename ifoo to igoo

* Add back BOMs

These tests were all using WpfFact, but not actually doing anything
that required either WPF or an STA thread. We plan to enable
parallelization of Facts (but not WpfFacts), and this ensures we can
parallelize as many tests as possible.

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

The SyntacticClassifierTests all need to be WpfFact due to their dependency on STA threads.  This was causing sporadic test failures in Jenkins.