[safe-browsing] Mechanical cleanups to tests and naming.

[safe-browsing] Mechanical cleanups to tests and naming.

Pull out and extend a bunch of mechanical changes from:
  https://codereview.chromium.org/220493003/
in hopes that the actual functional changes will be cleaner.

This includes:
 - cached_hits -> cache_hits
 - cached_hashes -> cache_hits
 - ASSERT_TRUE(UpdateStarted()) in db tests.
 - *_EQ() has expected value on the left in db tests.
 - ASSERT to check container sizes before dereferencing in db tests.
 - Compare list names as strings in db tests.
 - Consistently use prefix_hits for prefix hits in db tests.
 - Check prefix_hits before cache_hits in db tests.
 - Remove unused cache-related code from browser test.

BUG=357763

Review URL: https://codereview.chromium.org/283873002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270335 0039d316-1c4b-4281-b951-d872f2087c98