Update ID3 cues to span until playlist end, or next cue with same tag type (value.key) on cue append

[robwalch]

This PR will...

Update ID3 cues in timed metadata text tracks to span until the playlist end or until the start of the next cue with the same frame type.

Why is this Pull Request needed?

This change improves the handling of ID3 metadata for applications using metadata TextTrack active cues. Since ID3v2 frames have no duration or end time, cues should remain active until the HLS playlist's end or until another cue with the same ID3 frame type begins.

Are there any points in the code the reviewer needs to double check?

In Safari, DataCues are assigned an endTime of Infinity, but since HLS.js may use VTTCues, which must have finite start and end times, the current playlist end time was chosen to keep the number of active cues manageable. Applications wishing to modify the default endTime of new cues may do so on "cuechange".

Resolves issues:

Resolves #3879

Checklist

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• API or design changes are documented in API.md

[gkatsev]

Technically, a VTTCue is no longer needs to be bounded, as of w3c/webvtt#493. But it doesn't seem like this rolled out into any browser yet. Though, choosing the max time seems reasonable as an alternative.