Opensource a test tool called EditTextVariations

This CL opensouces a testing tool called EditTextVariations that has
been used internally to test IME behaviors on various
EditorInfo#inputType and EditorInfo#imeOptions.

Bug: 80039502
Test: Manually verified as follows.
 1. tapas EditTextVariations
 2. make -j
 3. adb install -r $ANDROID_TARGET_OUT_TESTCASES/EditTextVariations/EditTextVariations.apk
Change-Id: Ia87e655573c2fd1fc09d56e4af90bfb1dfd65f9b