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).