Convert most references to ReSpec's shortlinks syntax

[tidoust]

This pull request converts most of the occurrences of def-id in the spec to ReSpec's shorthands syntax. Motivation behind the changes:

• Makes the source slightly more readable and easier to edit (wrapping characters are still needed but no need to deal with IDs anymore or no need to add custom code).
• Less maintenance on custom script.
• The "right" version of external specs gets used, e.g the HTML LS instead of HTML5.1, or the ED of WebIDL instead of the published version.
• ReSpec computes references to a dfn, showed in a popup window when one clicks on a definition.
• It will be easier to detect terms from external specs that no longer exist or that these specs don't "export".

The pull request is rather large, but a commit approach should ease the review:

1. https://github.com/w3c/media-source/commit/14fc4aeda188a217dfa0a8bbc2f6c10a3f4bd8cb makes manual updates to the source to prepare for the conversion.
2. https://github.com/w3c/media-source/commit/281fe9c05ca36e2537a8934d6aa07d9c21b472ed applies a conversion script to the prepared source to convert all def-id occurrences that can be easily processed automatically.
3. https://github.com/w3c/media-source/commit/525d2e5fb50d104987323666f67ffcf9dce16320 drops the entries from media-source.js that are no longer needed after the conversion, leaving only those that still need to be converted AND those that byte stream format specs still reference so that these specs still render properly while they get updated.

The conversion leaves about 150 occurrences of def-id (out of the 1200 initial ones) that will still need to be addressed over time. They correspond to terms in external specs that are not yet part of the xref database used by ReSpec for some reason (terms in File API, some enum values and internal terms in the HTML spec), or to terms that need some custom logic.

The whole thing is purely editorial.

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Preview | Diff

[saschanaz]

LGTM to me, @wolenetz could you review this while you are at it? (I mean, you just found #270 😀)

[wolenetz]

I expect to review this one tomorrow. Thank you for doing this, @tidoust ! -- Update: Still reviewing the 3 pieces. No issues so far and if none found, may rebase and land tomorrow. I'll update again.

[tidoust]

I rebased the pull request against the main branch and forced pushed an update.

(There's a hiccup in the first commit where the end of the document gets duplicated for some reason. That's fixed in the second commit)

[wolenetz]

@ https://github.com/w3c/media-source/pull/265#event-4656732602 - thank you, I'll get back to work on this review today. I've been out of office.