Support priority based dumpsys in surface flinger

Call dump with no args when called with CRITICAL priority. Register
service with support for critical priority dumps.

BUG: 31774394

Test: adb bugreport ~/tmp.zip
Test: adb shell dumpsys --priority CRITICAL
Test: mmm -j32 frameworks/native/services/utils && \
      adb sync data && adb shell /data/nativetest/prioritydumper_test/prioritydumper_test && \
      adb shell /data/nativetest64/prioritydumper_test/prioritydumper_test && \
      printf "\n\n#### ALL TESTS PASSED ####\n"

Change-Id: I29140808493eb7c8805bfa338ab9a335154862b4