Statsd: apex modules in uid map

Fetch apex modules when getting all uids. Also moves the fetch from
third party apps can run to on boot completed to avoid increasing boot
time. This has some risk in that non-AID modules that log to statsd will
get dropped until boot completes, as we check the uidmap for
whitelisting of non-AID modules.

Test: adb shell cmd stats print-uid-map contains apex (tzdata, resolv)
Test: statsd_test
Test: atest google/perf/boottime/boottime-test -v
Bug: 130773130
Change-Id: I7c48b661f05a28a9b81036cf02ca36bb092a5743