Allow output from DumpController to be filtered

Dumpables must specify a _tag_ when registering. Tags can be selectively
filtered using:

  adb shell dumpsys activity service com.android.systemui/.SystemUIService \
    dependency DumpController tag1,tag2,tag3

Test: manual, atest
Change-Id: I85e26d1b8bdeffc401b3c80197d887bb021d35eb