[embedding][XWALK-2763] Add test cases for EmbeddingApi

- Add 2 cases for XWalkView.getRemoteDebuggingUrl
- Add 1 case for XWalkResourceClient.onReceivedSslError
- Failure analysis: the remoteDebuggingUrl returned is null

Impacted tests(approved): new 3, update 0, delete 0
Unit test platform: [Android]
Unit test result summary: pass 2, fail 1, block 0
And here.