[embedding][XWALK-1040] Add new embedding api tests for crosswalk

- Add 25 cases about tests for embedding api. 11 of them are for XWalkExtension interface, others are for XWalkUIClient interface.
- Failure analysis:6 cases are failed because the methods of embedding api are not exist.

Impacted tests(approved): new 25, update 0, delete 0
Unit test platform: [Android]
Unit test result summary: pass 19, fail 6, block 0