Use mVerb to track job execution state in system for consistency.

System currently uses `mRunningJob` to track job execution as a
simple binary (executing/not executing) state. However, `mRunningJob`
doesn't accurately reflect transient states, such as during initial
binding for `onStartJob` or when stopping due to `onStopJob`. These
granular state changes, from non-executing to executing, are tracked by
`mVerb`. While `mRunningJob` is functional, using `mVerb` for
consistency with other job related API implementation related to job
state checks would provide a more accurate and consistent reflection of
the job's lifecycle within the system.

Test: atest CtsJobSchedulerTestCases
Test: atest FrameworksMockingServicesTests
Bug: 372529068
Flag: android.app.job.handle_abandoned_jobs

Change-Id: Ib8077f601b9f476a71bbb1bd948aba4698d2fbc2