Slightly more efficient job storage.

Use binary XML:
- less space on disk: 500 jobs file size 99093b vs 177982b
- slightly better reading times: see perf test,
- less memory usage: 2.7M (https://pprof.corp.google.com/?id=ab851a8e29fa10e4e31635d9b7219be5&tab=tree&focus=writeJobsMapImpl) vs 130K (https://pprof.corp.google.com/?id=41244f6c3fa65f54b930087939a28231&tab=tree&focus=writeJobsMapImpl).

BEFORE:
[1/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_badRTC: PASSED (20.018s)
	testPersistedJobReading_fewJobs_badRTC_mean: 4403782
	testPersistedJobReading_fewJobs_badRTC_mean: 4329086
	testPersistedJobReading_fewJobs_badRTC_mean: 4361577
[2/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_manyJobs: PASSED (20.894s)
	testPersistedJobWriting_manyJobs_mean: 33269431
	testPersistedJobWriting_manyJobs_mean: 32886187
	testPersistedJobWriting_manyJobs_mean: 33093695
[3/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_goodRTC: PASSED (20.822s)
	testPersistedJobReading_manyJobs_goodRTC_mean: 39305058
	testPersistedJobReading_manyJobs_goodRTC_mean: 38768541
	testPersistedJobReading_manyJobs_goodRTC_mean: 38944530
[4/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_fewJobs: PASSED (21.046s)
	testPersistedJobWriting_fewJobs_mean: 4301181
	testPersistedJobWriting_fewJobs_mean: 4164938
	testPersistedJobWriting_fewJobs_mean: 4146446
[5/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_goodRTC: PASSED (21.137s)
	testPersistedJobReading_fewJobs_goodRTC_mean: 4230574
	testPersistedJobReading_fewJobs_goodRTC_mean: 4184341
	testPersistedJobReading_fewJobs_goodRTC_mean: 4192015
[6/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_badRTC: PASSED (21.016s)
	testPersistedJobReading_manyJobs_badRTC_mean: 39166861
	testPersistedJobReading_manyJobs_badRTC_mean: 39049685
	testPersistedJobReading_manyJobs_badRTC_mean: 38929124

AFTER:
[1/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_badRTC: PASSED (19.525s)
	testPersistedJobReading_fewJobs_badRTC_mean: 4082319
	testPersistedJobReading_fewJobs_badRTC_mean: 4067636
	testPersistedJobReading_fewJobs_badRTC_mean: 4066729
[2/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_manyJobs: PASSED (20.965s)
	testPersistedJobWriting_manyJobs_mean: 32787281
	testPersistedJobWriting_manyJobs_mean: 32545741
	testPersistedJobWriting_manyJobs_mean: 33066635
[3/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_goodRTC: PASSED (20.917s)
	testPersistedJobReading_manyJobs_goodRTC_mean: 36971876
	testPersistedJobReading_manyJobs_goodRTC_mean: 36671859
	testPersistedJobReading_manyJobs_goodRTC_mean: 37033008
[4/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobWriting_fewJobs: PASSED (21.171s)
	testPersistedJobWriting_fewJobs_mean: 4271303
	testPersistedJobWriting_fewJobs_mean: 4205693
	testPersistedJobWriting_fewJobs_mean: 4135812
[5/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_fewJobs_goodRTC: PASSED (20.992s)
	testPersistedJobReading_fewJobs_goodRTC_mean: 3914909
	testPersistedJobReading_fewJobs_goodRTC_mean: 3897198
	testPersistedJobReading_fewJobs_goodRTC_mean: 3932903
[6/6] com.android.frameworks.perftests.job.JobStorePerfTests#testPersistedJobReading_manyJobs_badRTC: PASSED (20.995s)
	testPersistedJobReading_manyJobs_badRTC_mean: 37105827
	testPersistedJobReading_manyJobs_badRTC_mean: 36804174
	testPersistedJobReading_manyJobs_badRTC_mean: 36943056

Bug: 135200955
Fixes: 135200955
Test: atest CtsJobSchedulerTestCases JobStoreTest JobStorePerfTests
Change-Id: I611c6fb8df029050a7e3ee300547152016a08f5c