stream-bundle: properly process requirements When the manifest bundle constain some known requirement that does not affect the stream clone, we used to crash. However since we know them and know they don't affect the stream clone, we can ignore them. Mozilla generated such buggy manifest bundle for a time which allowed us to catch this error. The issue was not caught until 961900fbd67c (released in 6.9.2) as the requirements information were ignored for stream-v2 until then. We fix the issue, refactor the code for robustness and adds more tests to better catch this kind of issue in the future.