Stop uploading results to webkit-perf.appspot.com
https://bugs.webkit.org/show_bug.cgi?id=110954

Reviewed by Benjamin Poulain.

When the specified test results server was webkit-perf.appspot.com, replace it by perf.webkit.org.
Also, always use the new JSON format. Removed the code to generate the old format.

* Scripts/webkitpy/performance_tests/perftestsrunner.py:
(PerfTestsRunner._generate_and_show_results):
(PerfTestsRunner._generate_results_dict):
(PerfTestsRunner._merge_slave_config_json):
(PerfTestsRunner._generate_output_files):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@144155 268f45cc-cd09-0410-ab3c-d52691b4dbfc