[Android] Add the instrumentation test for runtime client.

This instrumentation test contains the embedded and shared client.
For embedded client test:
  1. install XWalkRuntimeClientEmbeddedShell.apk
  2. build/android/run_instrumentation_tests.py \
     --test-apk XWalkRuntimeClientEmbeddedTest --verbose -I

For shared client test:
  1. install XWalkRuntimeLib.apk
  2. install XWalkRuntimeClientShell.apk
  3. build/android/run_instrumentation_tests.py \
     --test-apk XWalkRuntimeClientTest --verbose -I