Migrate typing logic from UiBench app to UiBenchMicrobenchmark test

With CL[1], we can simply remove the typing logic in
EditTextTypeActivity and also revert CL[2] logic without worrying the
apk signing problem and permission check for injectInputEvent.

[1]: I443f67748dfd3db0deb4cd12ac068975fbebc2c3
[2]: Id3c3490d7ab98a17da4e07d8d62d048c98ff1ec4

Bug: 289210988
Test: atest UiBenchEditTextTypingMicrobenchmark
Test: pts-tradefed run commandAndExit pts-postsubmit-very-long -m PtsUiBench \
   --fastboot-command-preparer:disable  \
   --log-level-display verbose -l VERBOSE \
   --test-arg com.android.tradefed.testtype.AndroidJUnitTest:instrumentation-arg:iterations:=1 \
   --test-arg com.android.tradefed.testtype.AndroidJUnitTest:class:\
   com.android.uibench.microbenchmark.UiBenchEditTextTypingMicrobenchmark#testEditTextTyping

Change-Id: I9a3b6a2a3df101bbd4dba9880944e8b83eb14610