Move more logic from handler classes to model classes and add unit tests

Move more logic from handler classes to model classes and add unit tests
https://bugs.webkit.org/show_bug.cgi?id=78989

Reviewed by Hajime Morita.

Extracted various functions from CreateHandler, ReportHanlder, and RunsHanlder to model classes
in order to unit-test them, added DataStoreTestsBase to reduce the code duplication in tests,
and added a whole bunch of unit tests in models_unittest.py.

* Websites/webkit-perf.appspot.com/create_handler.py:
(CreateHandler._create_branch):
(CreateHandler._create_platform):
* Websites/webkit-perf.appspot.com/models.py:
(_create_if_possible):
(_create_if_possible.execute):
(Branch):
(Branch.create_if_possible):
(Platform):
(Platform.create_if_possible):
(Build):
(Build.get_or_insert_from_log):
(Test):
(Test.update_or_insert):
(Test.update_or_insert.execute):
(TestResult):
(TestResult.get_or_insert_from_parsed_json):
(TestResult.get_or_insert_from_parsed_json._float_or_none):
(TestResult.generate_runs):
* Websites/webkit-perf.appspot.com/models_unittest.py:
(DataStoreTestsBase):
(DataStoreTestsBase.assertThereIsNoInstanceOf):
(DataStoreTestsBase.assertOnlyInstance):
(DataStoreTestsBase.assertEqualUnorderedList):
(HelperTests):
(HelperTests.test_create_in_transaction_with_numeric_id_holder):
(HelperTests.test_failing_in_create_in_transaction_with_numeric_id_holder):
(HelperTests.test_raising_in_create_in_transaction_with_numeric_id_holder):
(HelperTests.test_delete_model_with_numeric_id_holder):
(BranchTests):
(BranchTests.test_create_if_possible):
(PlatformTests):
(PlatformTests.test_create_if_possible):
(BuilderTests):
(_create_some_builder):
(BuildTests):
(BuildTests.test_get_or_insert_from_log):
(TestModelTests):
(TestModelTests.test_update_or_insert):
(TestModelTests.test_update_or_insert_to_update):
(TestResultTests):
(TestResultTests._create_build):
(TestResultTests.test_get_or_insert_value):
(TestResultTests.test_get_or_insert_stat_value):
(TestResultTests._create_results):
(TestResultTests.test_generate_runs):
(ReportLogTests):
(ReportLogTests.test_branch):
(ReportLogTests.test_platform):
(PersistentCacheTests):
(PersistentCacheTests.setUp):
(PersistentCacheTests.test_set):
* Websites/webkit-perf.appspot.com/report_process_handler.py:
(ReportProcessHandler.post):
* Websites/webkit-perf.appspot.com/runs_handler.py:
(RunsHandler.get):
(RunsHandler.post):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@108270 268f45cc-cd09-0410-ab3c-d52691b4dbfc