Fix for aligning live alt audio and subtitle playlists on msn without PDT

[robwalch]

This PR will...

Keep a reference to the last loaded level or track playlist object, and use it when aligning live playlists without PDT.

Why is this Pull Request needed?

Track group id changes replace track list, making it impossible to access the level or details object used prior to the switch using level[index].

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

Resolves issues:

Resolves #5802

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

[rajeshdish]

Seeing regression With this MR
Everytime we seek backwards we have to provide new URL to player, we call stopLoad> loadSource(with new URL)
during this time we are seeing this error and loadSource is not working (in playback only one segment keep repeating itself with freezes)

All fragments start & end time is in negative values

[rajeshdish]

this delta is going negative values (eg: -3232 | -2332)
with this changes playback started to work.

OR

[rajeshdish]

@robwalch ^^

[robwalch]

@rajeshdish,

Please fill out the Bug Report Template as part of your issue, making sure to include:

• Test stream/page (if possible)
• Steps to reproduce
• Expected behavior
• Actual behavior

If the issue is related to your stream, and you cannot share the stream, please include all the information we would need to reproduce the issue. This includes how to generate a stream that reproduces the issue.