[Web API] Flip pref for User defined byte streams

[hamishwillee]

Acceptance Criteria

• The listed features are documented sufficiently on MDN
• BCD is updated
• Interactive example and data repos are updated if appropriate
• The content has been reviewed as needed

For folks helping with Firefox related documentation

• Set bugs to dev-doc-complete
• Add entry to Firefox release notes if feature is enabled in release
  or
• Add entry to Firefox experimental features page if feature is not yet enabled in release

Features to document

Related Gecko bugs

https://bugzilla.mozilla.org/show_bug.cgi?id=1767342

Other

This flips dom.streams.byte_streams.enabled to true in FF102. More investigation needed.

There are docs in https://nodejs.org/api/webstreams.html#readablestreambyobrequestrespondbyteswritten too which might be help in understanding this.

[hamishwillee]

Affected APIs - note, in particular related to where the enable shown in BCD.

• ReadableByteStreamController
• ReadableStreamBYOBReader
• ReadableStreamBYOBRequest

These appear to have partial documentation. Minimally need to start by removing the experimental tagging on these.

There are missing methods, no examples and no real overview.

[hamishwillee]

Status

• BCD
  • FF102 User-defined byte-streams enabled browser-compat-data#16478
  • FF102 readable stream releaseLock() rejects pending read requests browser-compat-data#16919
• Docs
  • FF102 User define byte stream interface - not experimental #16818
  • Add missing methods FF102 User define byte stream interface - not experimental #16818
  • Add class/method example code
  • Add guide
• Release notes
  • FF102 Relnote: Readable byte streams #17363
  • Updated release note with new link ReadableStream reader - releasing lock throws pending read #18241
• dev-doc-complete

All done bar some BCD and docs "tidy" to reflect changes in spec related to releaseLock()