Split up testHelpers.inc, break off fuzz testing

Split up testHelpers.inc, break off fuzz testing

* Split up testHelpers.inc into one class per file, with the file named
  after the class per the usual convention. Put them in tests/parser
  since they are all parser-related, even though a couple are reused by
  other unit tests.
* Also rename parserTest.inc and parserTestsParserHook.php to follow the
  usual convention, and split off ParserTestResultNormalizer
* Move fuzz testing out to its own maintenance script. It's really not
  helpful to have fuzz testing, which is designed to run forever,
  exposed as a PHPUnit test.
* Increased fuzz test memory limit, and increased the memory headroom for
  getMemoryBreakdown(), since HHVM's ReflectionClass has an internal
  cache which uses quite a lot of memory.
* Temporarily switched a couple of ParserTest methods from private to
  public to support fuzz testing from a separate class -- I plan on
  replacing this interface in a subsequent commit.

Change-Id: Ib1a07e109ec1005bff2751b78eb4de35f2dfc472