- Eliminate stubs with a variable number of arguments.
  (That only worked due to their very limited use. These
   stubs' interface descriptors were basically lying
   about their number of args, which will fail when used
   generically.)
- Fix all CallApi*Stubs' interface descriptors to no
  longer lie about their arguments.
- Unify CallApi*Stub, for * in Function, Accessor,
  FunctionWithFixedArgs.
  (Since these are now all doing the same thing.)
- Rename the unified stub (and interface descriptors) to
  *ApiCallback*, since that's really what they're doing.
- Refuse inlining an API callback if its number of
  parameters exceeds the supported number of args.

BUG=

Review URL: https://codereview.chromium.org/1748123003

Cr-Commit-Position: refs/heads/master@{#34614}