- add new code to PatternCleanup.rewriteAST() to create a static field
  when the regex is a StringLiteral and not inside a static initializer
  nor a non-static inner class nor an interface default method
  nor a local class
- remove getResult() from PatternOperation so multiple cleanups can be
  performed in a single block
- change regex tests in CleanupTest to add fields where appropriate
  and add new tests

Change-Id: Id81b7448be0c08478d7103d9b204c450b11e583a