Extend JobInfo to support NetworkRequest.

The current JobInfo.NETWORK_TYPE values offer basic network selection
ability, but more precise requirements continue to come up.  Instead
of creating more NETWORK_TYPE constants, add support for the existing
NetworkRequest object, which is the idiomatic way for an app to
express the type of network they'd like to use.

Move the implementation details of NETWORK_TYPE constants to use this
new NetworkRequest functionality.  Deprecate NETWORK_TYPE_METERED,
since the lack of the NOT_METERED capability doesn't imply that the
connection is metered.  (Apps using this API to get to a cellular
network should use TRANSPORT_CELLULAR instead.)

Add new SystemClock APIs that return java.time.Clock instances for
various Android-specific clocks.  This gives us a clean interface
(with negligible overhead) for swapping in artificial clocks for
testing purposes.

Improve JobStoreTest to validate new NetworkRequest features, and
add one last sanity check to assertTasksEqual() to compare raw
bits-on-wire, to catch people who forget to check new fields.  Watch
for IoThread to go idle to run tests faster.

Test: bit FrameworksServicesTests:com.android.server.job.
Bug: 67040695
Change-Id: I189e7602132a0ec26d2f0cc6dadc188664961a47