rtmp-services: Add Enhanced Streaming support for PandaTV

[lmg2530]

Description

• Add support for eRTMP multitrack video configuration URL to rtmp-services

Motivation and Context

• Twitch/Amazon IVS uses server side configuration for eRTMP Enhanced Broadcasting/multitrack video stream configuration, so users don't have to manually configure renditions being sent.

• Add Enhanced Streaming support for pandatv

How Has This Been Tested?

• This is in use in the Twitch Enhanced Broadcasting Beta

Types of changes

• New feature(non-breaking change which adds functionality)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.

[Fenrirthviti]

Looks fine, though I did not fully test the ladder configs as I do not have access to a full range of possible hardware and software encoders that might be present.

That said, from a process standpoint, I don't know that it's worth us trying to vet and provide feedback on the actual configurations, so this seems fine to me.