feat: AndroidUrlMediaSource, Tests, Comments and Refactoring for MediaSourceConfiguration classes.

[SureshkumarKV]

Issue #, if available: No GitHub issues, but this is a production issue I have helped a customer with. This PR is based on the solution I gave to the customer and the same has been tested and verified by the customer as well.

Description of changes: Recently, we had a customer who wanted to use video files/urls as the source instead of camera. This solution implements a new AndroidUrlMediaSource class to facilitate this. Apart from this class, a number of supporting changes also had to be added such as extracting common code in MediaSourceConfiguration into AbstractMediaSourceConfiguration class. I have also added extensive code documentation for all new and exisiting files that were modified.

Kindly review, as this can help a lot of customers.

Please let me know if there are questions, suggestions for change etc.

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