Add perf tests for JobStore file reading & writing.

1. Add perf tests to evaluate changes to JobStore's persisted file reading
and writing.

2. Renaming parameters to make it clearer what they're for.

3. Removing targetSdkVersion from JobStatus because it's not being used and
made testing a little harder.

Current results (times are in nanoseconds):

JobSchedulerPerfTests (6 Tests)
------------------------------
[1/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_badRTC: PASSED (37.082s)
	testPersistedJobReading_fewJobs_badRTC_median: 16333804
	testPersistedJobReading_fewJobs_badRTC_percentile95: 17523439
	testPersistedJobReading_fewJobs_badRTC_stddev: 1402393
	testPersistedJobReading_fewJobs_badRTC_percentile90: 17523439
	testPersistedJobReading_fewJobs_badRTC_mean: 16193033
[2/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_manyJobs: PASSED (42.610s)
	testPersistedJobWriting_manyJobs_stddev: 47895383
	testPersistedJobWriting_manyJobs_percentile95: 235706638
	testPersistedJobWriting_manyJobs_median: 214356219
	testPersistedJobWriting_manyJobs_percentile90: 235706638
	testPersistedJobWriting_manyJobs_mean: 197006269
[3/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_goodRTC: PASSED (40.855s)
	testPersistedJobReading_manyJobs_goodRTC_percentile95: 107394438
	testPersistedJobReading_manyJobs_goodRTC_mean: 96397639
	testPersistedJobReading_manyJobs_goodRTC_median: 95545374
	testPersistedJobReading_manyJobs_goodRTC_percentile90: 107394438
	testPersistedJobReading_manyJobs_goodRTC_stddev: 7879676
[4/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_fewJobs: PASSED (37.131s)
	testPersistedJobWriting_fewJobs_percentile90: 18209220
	testPersistedJobWriting_fewJobs_stddev: 2401331
	testPersistedJobWriting_fewJobs_percentile95: 18209220
	testPersistedJobWriting_fewJobs_median: 13676251
	testPersistedJobWriting_fewJobs_mean: 14685137
[5/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_goodRTC: PASSED (37.170s)
	testPersistedJobReading_fewJobs_goodRTC_median: 13792865
	testPersistedJobReading_fewJobs_goodRTC_mean: 15065688
	testPersistedJobReading_fewJobs_goodRTC_percentile90: 19445106
	testPersistedJobReading_fewJobs_goodRTC_percentile95: 19445106
	testPersistedJobReading_fewJobs_goodRTC_stddev: 3025478
[6/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_badRTC: PASSED (40.725s)
	testPersistedJobReading_manyJobs_badRTC_percentile90: 96233552
	testPersistedJobReading_manyJobs_badRTC_stddev: 6633074
	testPersistedJobReading_manyJobs_badRTC_mean: 89815566
	testPersistedJobReading_manyJobs_badRTC_median: 91038758
	testPersistedJobReading_manyJobs_badRTC_percentile95: 96233552

Bug: 135200955
Test: atest com.android.frameworks.perftests.job.JobStorePerfTests
Test: atest com.android.server.job.JobStoreTest
Test: atest com.android.server.job.controllers.ConnectivityControllerTest
Test: atest com.android.server.job.controllers.JobStatusTest
Test: atest com.android.server.job.controllers.QuotaControllerTest
Change-Id: Id5cc72d6703b2b1c5d553de91b8a1837b360bc7f