This wasn't included in the project file, so clearly wasn't being used.

This is a (currently empty) project that will contain parts of
EditorFeatures that demand the WPF surface area.

* Adding cobyrc file for testing

* Adding isImplicit info to ioperation tests

* Adding Language name to the test dumper

* Formatting change to test dumper

* Removing cobyrc file

* Fixing more tests

* Resolving conflicts

* Moving the language to assert check

* Resolving conflicts

* Reacting to merge conflict

Fixes #21768
Fixes #22027

Reduce DocumentId array allocations

Since ImmutableDictionary and ImmutableSortedDictionary are both
implemented via trees; you can think of an ImmutableDictionary as just
being a sorted dictionary where the underlying key is the hash int.
Since our hash is just a hash of a GUID, we can compare by the GUID,
switch to a ImmutableSortedDictionary, and then avoid another sort
when we're computing checksums.

Bump NuGet monikers for the preview 1 split

There is no conversion between ref like types and either object or generic parameters (even if constrained to struct) in either direction. This change enforces that rule and adds tests around pattern matching, which exercises this rule.

We previously were using ImmutableArrays, so if you had a large number
of documents (say thousands) we'd be creating huge numbers of huge
arrays over and over again. For this pattern, ImmutableList is more
appropriate.

Fix bug in build-utils Ensure-SdkInPathAndData

Add unit tests for omitted arguments

Add unit tests for IArrayElementReferenceExpression and make the API …

Most constructs already had tests, but I added a few more just in case.
Although Span return in iterators is currently impossible because no
ref-struct capable type can be an iterator, I added a safety check in
case we allow it later.

Fixes #22305

Temporarily moves checks for `partial` back into the parser.

Fixes #22379

Fixes #18348

Fixes #22244
Related to #22406

* updated local decl

* put IVariableDeclarationStatement back to for loop before.

* put variable declaration syntax in variable declaration statement for for loop

* updated tests

* changed caller to call different APIs to create variable declaration when it can.

* changed to return IVaraibleDeclaration from CreateVariableDeclaration method

* addressed PR feedbacks

* Clean up

* Test fixes

* Fix failing test

Allow "in" at call sites as a way to request strict "in" parameter passing.

- "in" argument matches only "in" parameters (as opposed to unmodified case that can also match byval parameters)
- "in" requires that the argument is an lvalue
- "in" does not allow conversions at the call-site other than identity conversions
- "in" sets an exact bound in generic method type inference
- "in" cannot be stack-spilled by value

move designer attribute back to document level scanner but made it to use keep alive connection rather than creating new connection every time. also kept some optimization such as checking cps projects or not reporting as much as we can. (#22248)

Skip DeconstructionAssignmentWithRefReadonlyExtension unit test