Expression parsing comments.

Consistency with Roslyn.  The 'type' shape of the nodes makes it clear what they are.  If there is ambiguity (for example, a node with multiple cihldren of the same type), then a disambiguating term is used.  I don't believe there is value in us having multiple MS language APIs that follow different naming conventions.  (unless there is a specific *per language* reason to differentiate).  In this case, there is no reason to treat TS/JS different here from C#/VB.