Add a new flag to dump normal priority content from ActivityManagerService

- remove cloned logic from main dump function

Bug: 31774394
Test: adb bugreport ~/tmp.zip
Test: adb shell dumpsys activity -a > activity_legacy.dump && adb shell dumpsys activity -a --dump-priority NORMAL > activity_split.dump && adb shell dumpsys activity --dump-priority CRITICAL >> activity_split.dump && diff activity_legacy.dump activity_split.dump
Change-Id: Iebec9f5bd9215efbb6f66bc4eb8b389b1dbb8bf9