Handle PTS rollover on initial sample of video or audio

[robwalch]

This PR will...

Normalize first audio and video PTS/DTS when comparing the two and determining initPTS to ensure elementary media streams are aligned on start.

Why is this Pull Request needed?

In a stream where the first video PTS is a wrapped unsigned integer as seen below, we don't want to base initPTS on this value and attempt to align audio to it.

videoTrack.samples
0: {key: true, pts: 8589933243, dts: 8589933243, units: Array(3), debug: "", …}
1: {key: false, pts: 1711, dts: 1711, units: Array(1), debug: "", …}
2: {key: false, pts: 4681, dts: 4681, units: Array(1), debug: "", …}
3: {key: false, pts: 7651, dts: 7651, units: Array(1), debug: "", …}
4: {key: false, pts: 10711, dts: 10711, units: Array(1), debug: "", …}
5: {key: false, pts: 13681, dts: 13681, units: Array(1), debug: "", …}
6: {key: false, pts: 16651, dts: 16651, units: Array(1), debug: "", …}

audioTrack.samples
0: {unit: Uint8Array(243), pts: 1, dts: 1}
1: {unit: Uint8Array(243), pts: 1921, dts: 1921}
2: {unit: Uint8Array(244), pts: 3841, dts: 3841}
3: {unit: Uint8Array(265), pts: 5761, dts: 5761}
4: {unit: Uint8Array(242), pts: 7681, dts: 7681}
5: {unit: Uint8Array(255), pts: 9601, dts: 9601}
6: {unit: Uint8Array(243), pts: 11521, dts: 11521}

Resolves issues:

#3082

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

[robwalch]

@stevendesu please have a look at this fix and let me know if it resolved #3082 for you.