[webapi] Add 1 TC and delete duplicated files in tct-fileapi-w3c-tests

Impacted Suites: tct-fileapi-w3c-tests
Impacted TCs num: New 1, Update 0, Delete 3
Unit test platform: IVI
IVI test result summary: Pass 1, Fail 0, Blocked 0

Add Reason:
Add 1 TC for missing test point.

Remove TC check point repeat:
Remove new-Blob.html file due to it is duplicated by Blob-constructor.html file.

Remove files check point is not about fileapi:
URL_exists.html
BlobBuilder.html