fix(net): Remove AbortController polyfill

[tykus160]

AbortController polyfill attaches to the global object and it messes up with feature detection for projects that are using shaka. As it is not able to properly abort ongoing requests, it doesn't give much value.

[avelad]

@shaka-bot test

[shaka-bot]

@avelad: Lab tests started with arguments:

• pr=7149

[shaka-bot]

Incremental code coverage: 97.22%

[avelad]

i think that is necessary for hls parser, @joeyparrish i’m on holidays, can you review it? thanks!

[tykus160]

Ah sorry, I missed that. My point still stands though - shaka has network abstraction layer and PendingRequest class inherits AbortableOperation with an abort() method. We should use this in that case, not AbortController. I'll try to update this PR.

[avelad]

@shaka-bot test

[shaka-bot]

@avelad: Lab tests started with arguments:

• pr=7149

[joeyparrish]

Not sure whether or not this is a mistake. Please take a look!

[joeyparrish]

The merge conflicts are trivial. I changed abort_controller.js in #7176 for an easy cherry-pick. You can just delete the updated version and merge.

[joeyparrish]

@tykus160, I have prepared new releases for v4.10.x and v4.9.x, but I will wait another day to see this get finished and merged.

[theodab]

I think this mostly looks good (besides Joey's comment).