migrate web-platform-tests and web-platform-test-reftests to osx 10.14.

Backed out for causing a spike in wpts and wpts reftests intermittents.

Push range with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=success%2Ctestfailed%2Cbusted%2Cexception&searchStr=macosx1014-64%2Cweb%2Cplatform&fromchange=4ff8006a80f54f8d5f6aebcbd89867e53a30f709&tochange=778464d9aac88b896b1f6901d1e7c6c6572f5929&selectedJob=250246996

Failure log:
https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=250246996&repo=autoland&lineNumber=1087
https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=250246404&repo=autoland&lineNumber=2215
some of the logs have exceeded the size limit and they were not parsed
Reftest analyzer:
https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://queue.taskcluster.net/v1/task/Rpz0R56SSdiN4G9AaOnVfQ/runs/0/artifacts/public/logs/live_backing.log&only_show_unexpected=1

Backout link: https://hg.mozilla.org/integration/autoland/rev/7fad4bfcc1deeaf461387c9f792f450186afd4ad

Backed out changeset 0cff8ca10f71 (Bug 1557123) for many wpt failures on osx 10.14

Push with failures: https://treeherder.mozilla.org/#/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel%2Crunnable&fromchange=91643c6f9a42b80a9e63db58931f8b4be8c6e69b&searchStr=macosx1014%2Cweb%2Cplatform%2Ctests&tochange=c5a178862298231ac3c47b6d4631a2df3c6499c6&selectedJob=250482970

Backout link: https://hg.mozilla.org/integration/autoland/rev/c5a178862298231ac3c47b6d4631a2df3c6499c6

Failures:
https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=250482970&repo=autoland&lineNumber=3089
22:43:43 INFO - TEST-START | /xhr/event-timeout.any.worker.html
22:43:43 INFO - Closing window 229780750337
22:43:44 INFO -
22:43:44 INFO - TEST-UNEXPECTED-FAIL | /xhr/event-timeout.any.worker.html | XMLHttpRequest: timeout event - assert_unreached: ontimeout not called. Reached unreachable code
22:43:44 INFO - @http://web-platform.test:8000/xhr/event-timeout.any.js:16:5
22:43:44 INFO - Test.prototype.step_timeout/<@http://web-platform.test:8000/resources/testharness.js:1652:22
22:43:44 INFO - Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:1594:25
22:43:44 INFO - Test.prototype.step_func/<@http://web-platform.test:8000/resources/testharness.js:1618:35
22:43:44 INFO - setTimeout handler*Test.prototype.step_timeout@http://web-platform.test:8000/resources/testharness.js:1651:16
22:43:44 INFO - @http://web-platform.test:8000/xhr/event-timeout.any.js:15:8
22:43:44 INFO - Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:1594:25
22:43:44 INFO - @http://web-platform.test:8000/xhr/event-timeout.any.js:4:6
22:43:44 INFO - @http://web-platform.test:8000/xhr/event-timeout.any.worker.js:8:1
22:43:44 INFO - TEST-OK | /xhr/event-timeout.any.worker.html | took 399ms

https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=250482956&repo=autoland&lineNumber=6543
22:38:02 INFO - TEST-START | /pointerevents/pointerlock/pointerevent_movementxy_when_locked.html
22:38:02 INFO - Closing window 6442450945
22:38:02 INFO - {'actions': [{u'type': u'pointer', u'actions': [{u'y': 0, u'x': 0, u'type': u'pointerMove', u'origin': {'element-6066-11e4-a52e-4f735466cecf': u'7c68e9ce-8610-a343-9554-d5d547553716', 'chromeelement-9fc5-4b51-a3c8-01716eedeb04': u'7c68e9ce-8610-a343-9554-d5d547553716'}}, {u'button': 0, u'type': u'pointerDown'}, {u'y': 0, u'x': 10, u'type': u'pointerMove', u'origin': {'element-6066-11e4-a52e-4f735466cecf': u'7c68e9ce-8610-a343-9554-d5d547553716', 'chromeelement-9fc5-4b51-a3c8-01716eedeb04': u'7c68e9ce-8610-a343-9554-d5d547553716'}}, {u'y': 0, u'x': 20, u'type': u'pointerMove', u'origin': {'element-6066-11e4-a52e-4f735466cecf': u'7c68e9ce-8610-a343-9554-d5d547553716', 'chromeelement-9fc5-4b51-a3c8-01716eedeb04': u'7c68e9ce-8610-a343-9554-d5d547553716'}}, {u'y': 0, u'x': 30, u'type': u'pointerMove', u'origin': {'element-6066-11e4-a52e-4f735466cecf': u'7c68e9ce-8610-a343-9554-d5d547553716', 'chromeelement-9fc5-4b51-a3c8-01716eedeb04': u'7c68e9ce-8610-a343-9554-d5d547553716'}}, {u'button': 0, u'type': u'pointerUp'}], u'parameters': {u'pointerType': u'mouse'}, u'id': u'mousePointer1'}]}
22:38:12 INFO -
22:38:12 INFO - TEST-UNEXPECTED-TIMEOUT | /pointerevents/pointerlock/pointerevent_movementxy_when_locked.html | mouse pointerevent movementX/Y when lock test - Test timed out
22:38:12 INFO - TEST-TIMEOUT | /pointerevents/pointerlock/pointerevent_movementxy_when_locked.html | took 10374ms

https://treeherder.mozilla.org/logviewer.html#/jobs?job_id=250482969&repo=autoland&lineNumber=4659
22:36:00 INFO - TEST-START | /pointerevents/extension/pointerevent_pointerrawupdate.html
22:36:00 INFO - Closing window 12884901889
22:36:01 INFO - {'actions': [{u'type': u'pointer', u'actions': [{u'y': 0, u'x': 0, u'type': u'pointerMove', u'origin': {'element-6066-11e4-a52e-4f735466cecf': u'c25aff57-95bc-1542-bc89-202ffaebd0d8', 'chromeelement-9fc5-4b51-a3c8-01716eedeb04': u'c25aff57-95bc-1542-bc89-202ffaebd0d8'}}, {u'button': 0, u'type': u'pointerDown'}, {u'button': 1, u'type': u'pointerDown'}, {u'button': 1, u'type': u'pointerUp'}, {u'button': 0, u'type': u'pointerUp'}], u'parameters': {u'pointerType': u'mouse'}, u'id': u'1'}]}
22:36:01 INFO -
22:36:01 INFO - TEST-UNEXPECTED-FAIL | /pointerevents/extension/pointerevent_pointerrawupdate.html | pointerrawupdate event received - assert_true: Pointerrawupdate event should have been received before pointermove. expected true got false
22:36:01 INFO - run/</<@http://web-platform.test:8000/pointerevents/extension/pointerevent_pointerrawupdate.html:38:25
22:36:01 INFO - Test.prototype.step@http://web-platform.test:8000/resources/testharness.js:1594:25
22:36:01 INFO - run/<@http://web-platform.test:8000/pointerevents/extension/pointerevent_pointerrawupdate.html:37:43
22:36:01 INFO - TEST-OK | /pointerevents/extension/pointerevent_pointerrawupdate.html | took 463ms

https://hg.mozilla.org/mozilla-central/rev/1580e2e6a87b