Fix failing puller unit tests

The unit tests relied on kPullAllAtomInfo containing the correct
information.
This static map is no longer correct, since pullers are registered, but
will not be registered in the test environment. This cl changes the map
to not be static, and for the pullers to contain their own metadata.

Test: bit statsd_test:*
Test: adb shell cmd stats pull-source (various atoms)
Test: atest GtsStatsdHostTestCases
Change-Id: I0555a5ab1b4d15a6cd0b0dbcd49d856c93de7aa6