[Proposal] Update mediaCapabilitiesProber API

[peaBerberian]

After some brainstorming related to #1470, we noticed that as is, our old mediaCapabilitiesProber experimental tool could gain by being more flexible.

Especially, the getCompatibleDRMConfigurations method checked multiple EME MediaKeySystemConfiguration at once and returned information on actual configurations compatible to them once all of them have been checked.

We wondered whether this method would not be more useful by making it less powerful: we'll now only check for a single MediaKeySystemConfiguration per method call (and rename that method to checkDrmConfiguration).
Doing this signals to an application that it can just combine multiple calls if it wants the old behavior (e.g. through a Promise.all), use Promise.race to just obtain the first one etc. (this would still be possible with the previous API, but seemed unnatural to application developers).

I also added a timeout argument to it, but realized that it might be very complex to maintain, as theoretically checkDrmConfiguration could call multiple browser API sequentially in the future (as other mediaCapabilitiesProber's methods are doing).
In that case, where are we supposed to apply the timeout: to each browser API call or globally on the method?

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I also profited from this work to rewrite the implementation of other mediaCapabilitiesProber's method without changing their API, as I found that a lot of its data-processing code was unneeded and difficult to follow.