IDL compiler: cleanup test cases

Just a cleanup:
* Remove [RuntimeEnabled] and [PerContextEnabled] from TestPartialInterface,
　as Perl behavior is wrong (not actually used).
* Slight rearrangement of templates to reuse exceptionState.

With these changes, the only remaining feature in TestInterface
is union types for special operations, which is next up!

R=haraken
NOTRY=true

Review URL: https://codereview.chromium.org/135553004

git-svn-id: svn://svn.chromium.org/blink/trunk@166226 bbb929c8-8fbe-4397-9dbb-9b2b20218538