* 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

* 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

Fixes:#22306

Fixes #22006

* Improve consistency of handling constant null switch expression
Fixes #20210
* Rationalize reachability for pattern switch.
If a single case could handle all inputs, e.g. has the
same constant value, a wildcard pattern, etc, then
the default label is considered unreachable.
The concept of reachability, which takes the value of the
switch expression into account and can produce warnings,
is separate from the concept of subsumption which takes
the full set of patterns into account and can produce errors.
* Document breaking change in pattern switch.
Alse change formatting as suggested in code review.

* ported tests from https://github.com/dotnet/roslyn/pull/21263

* added ref readonly test

* added more tests following PR suggestion

Fixes #22008

There might be some more API changes based on the open issues mentioned in #22008

Fixes #22265

Fixes #22007

Fixes #22003 and #21296.

reverted encoding only changes
marked as implicit for expression statement that doesn't point to expression syntax node
added tracking bug in the comment

addresses more PR feedbacks

Fixes https://github.com/dotnet/roslyn/issues/21748

I also found that Range and Relational case clause have no tests in VB. Additionally, I also marked all OperationAnalyzerTests with CompilerTrait attribute so they don't get skipped in local trait based testing.
Fixes #22129

Address feedback from Aleksey and generate a dynamic member reference expression for a bound method group that is a child of dynamic invocation

1. Fix test issues
2. Remove IHasDynamicArgumentsExpression interface and move the Arguments property from it to individual IDynamicXXXExpression nodes.
3. Adjust the extension methods for GetArgumentName and GetArgumentRefKind accordingly.

In preparation for a merge of features/ioperation to master, we have decided to internalize all the IOperation APIs which are either not tested or not reviewed by the design team.
This includes the following APIs with bugs tracking reviewing/adding tests for them: IArrayElementReferenceExpression(https://github.com/dotnet/roslyn/issues/22006), IAwaitExpression(https://github.com/dotnet/roslyn/issues/22007), ICatchClause(https://github.com/dotnet/roslyn/issues/22008), IEndStatement(https://github.com/dotnet/roslyn/issues/22004), IPlaceholderExpression(https://github.com/dotnet/roslyn/issues/21294), ISizeOfExpression(https://github.com/dotnet/roslyn/issues/21296), IStopStatement(https://github.com/dotnet/roslyn/issues/21297), ITryStatement(https://github.com/dotnet/roslyn/issues/22008), ITypeOfExpression(https://github.com/dotnet/roslyn/issues/22003), IWithStatement(https://github.com/dotnet/roslyn/issues/22005)

This change also includes a simple API rename: IMethodBindingExpression renamed to IMethodReferenceExpression(https://github.com/dotnet/roslyn/issues/21289).