Skip load app name from PackageManager while init the BatteryEntry.

- getApplicationLabel is time-consuming.
[Before]
https://pprof.corp.google.com/?id=bade2601da25f6169b0685a3e2a3e5cc
https://screenshot.googleplex.com/86R5DhMgcyQakys
[After]
https://pprof.corp.google.com/?id=2ccb1e88222e96db1fbcc072470a254c
https://screenshot.googleplex.com/7QviDFSpgzoQcg6

Bug: 349120408
Fix: 349120408
Test: atest + pprof
Flag: EXEMPT bug fix
Change-Id: I1eed60cea9c5bd3f77f38993f7d04906aa811da5