Rebased onto future branch
Fixed Tuple field signatures
Fixed tests affected by tuple parsing

Most interesting parts here are:
* the syntax node shape and naming - these are public APIs so we should get the naming right.
NOTE: I expect some churn here so for now I have disabled the public API diagnostics.

* parsing something that starts with "("  is tricky since that can be a start of many constructs - lambdas, casts, parenthesized expressions...
I have updated the lookahead logic that tries to figure what we are dealing with, but it may need some tuning to be more robust.
In particular there could be some error recovery work to see that handling of broken code is sensible.

==== Current assumptions:
1) TupleTypes and TupleExpressions must have 2 or more elements/arguments. However we may have to parse 0 and 1 sized expressions for error recovery reasons. Those are syntax errors.

2) TupleType looks like

(int x, int y)  x = ...

I.E.

  ( type [name], type [name])

We may enforce that all or no elements have names. Not sure yet if that needs to be in parser or binder.

3) TupleExpression looks like

var something = (x: foo(), y: bar);

I.E.

  ( [name:] expr, [name:] expr)

just like with the types we may want to enforce that all or none of the arguments have names. Not sure if that is a syntax or binding error.
It is not a part of this change.

This reverts commit 15488921.

harden both DetectTypeCircularity and GetDependenceChain

Only exception is params parameters, tracked by #10708.

Fixes #10389

* remove old syntax tree root tests

* fix vb tests

Ensure that we generated a CompilationCompletedEvent for compilations with no source files (example an empty VSIX projects).

This reverts commit 31377ce7.

This reverts commit 7debfc47.

This reverts commit a03d8b8e.

This reverts commit 359eba13.

Ensure that we generated a CompilationCompletedEvent for compilations with no source files (example an empty VSIX projects).

Update TargetFrameworkVersions.

This reverts commit a96d7825.

An ArrowExpressionClauseSyntax is special because it has an expression as its direct child. Because of that the binder was not correctly caching all nodes of the bound tree and instead was falling back to binding decendand nodes by themself when asked for them. This fails if in the decendant nodes there is a color color case.

With this change the binder does cache all of the ArrowExpressionClauseSyntax's children including the correctly resolved symbols for a color color situation.
Fixes #5362
Closes #8167

and for each one, either
1. address the issue, or
2. ensure that there is an issue tracking it

Move lines appearing in PublicAPI.Unshipped.txt files to
PublicAPI.Shipped.txt files and re-sort the latter.

Note: VB scripting APIs and APIs for IOperation continue to remain
unshipped.