[embedding][XWALK-2239] Add one usecase to verify animatible

- Add one usecase to verfiy animatible by leveraging developer's sample.
- Remove the redundant LoadAppFromManifestActivity.java and XWalkEmbeddingAPISample.java code.

Impacted tests(approved): new 1, update 0, delete 0
Unit test platform: [Android]
Unit test result summary: pass 1, fail 0, block 0