WriterTest: Add more tests

This CL changes the following things in the unit test

1. Add InvalidInputTest to validate writers for invalid inputs
2. Add new combination in Listener Test to increase code coverage
3. Add MalFormedDataTest to increase code coverage for MPEG4 Writer
4. Add Mpeg4WriterTest to increase code coverage for MPEG4 Writer

Test: atest writerTest -- --enable-module-dynamic-download=true

Line coverage increased from  66.2% to 71.6%
Funtion coverage increased from  78.5% to 84.5%

Bug: 159782681
Bug: 160125298

Change-Id: Ieed3494f2b5bfedf7e7426cdc51d2cd43e74c96a