Simplify TONATIVE_*_EXCEPTIONSTATE* macros

By assuming that the |value| expression throws exceptions via the
ExceptionState object, and only via it, we can skip the v8::TryCatch
declaration and check. This is good since it is less code, and since
v8::TryCatch objects cost a bit of CPU time to initialize.

The correctness of this patch depends on
  https://codereview.chromium.org/559553003/
and
  https://codereview.chromium.org/556273003/
that make sure all type conversion helpers with an ExceptionState&
argument actually throw all exceptions via it.

Review URL: https://codereview.chromium.org/552143004

git-svn-id: svn://svn.chromium.org/blink/trunk@181796 bbb929c8-8fbe-4397-9dbb-9b2b20218538