* Add native stacktrace field for PlatformException

* Mute the readValue check for stacktrace.

* polish

* Add unit test and further polish

* Added more comments

* remove unnecessary import

* fill in stacktrace to JSONMethodCodec and fix tests

* fix style

* Fix format

* Remove unnecessary TODO since not all explicitly declared errors have stacktrace in it from native side.

* Handle case for exception without stacktrace on jsonMethodCodec

* Add more unit tests

* format test
Co-authored-by: Ben Li <libe@google.com>