- Revived `RazorEditorParser`.
- Made `PartialParseResult` internal and renamed it to `PartialParseResultInternal`. This fell in line with other syntax tree types.
- Moved the `RazorEditorParser` implementation away from `TextChange` and `ITextBuffer`. Instead it now relies on `SourceChange` and the VS contract `ITextSnapshot`.
- Added `RazorEditorParserTest` to ensure the changes in implementation did not impact previous functionality.
- Removed some obvious tests that unnecessarily re-tested behavior that was already verified.
- Updated tests.
- Moved several Language.Test types to the common test project so they could be reused.
#1259
