Fix AppStartInfo ProcessRecord lookup

AppStartInfo is using package name for process record lookup, rather
than process name, for Activity component starts only. This results
in being unable to obtain the process record for activity based
starts for apps which set a process name, which subsequently causes
the start record to be discarded.

Bug: 443136429
Test: trigger activity starts for an app which overrides process name
  confirm using shell command that records are now added as expected.
Test: atest WmTests:ActivityMetricsLaunchObserverTests
Flag: com.android.server.am.app_start_info_process_name_fix
Change-Id: I6aa5c0962f3f64c5d28348ad0646f2a91f7f84f8