feat: single compose file including hwaccel

[mertalev]

Description

The hwaccel.*.yml files are separate for two reasons: to make it easier to set all the appropriate settings without missing anything or caring about the details, and to avoid cluttering the services with a bunch of commented lines.

However, the fact that they're separate files makes them inconvenient, and many platforms don't expose the ability to have multiple Compose files. Uncommenting the extends section and changing the right fields from cpu is simple but also somewhat awkward, and it becomes more awkward in a dev workflow as you have to stash and unstash changes.

This PR moves all of this into the same Compose file and makes it possible to set the transcoding and machine learning backends just through the IMMICH_TRANSCODING_BACKEND and IMMICH_MACHINE_LEARNING_BACKEND environmental variables. This makes it easier to configure with fewer steps, leaves less room for error, and makes it much more convenient for development.

The way it does this is crafty: it defines services for these configs, disables them by assigning a profile to them so they don't actually run, extends the server and machine learning services from the same Compose file, uses environmental variable interpolation in this extends section to allow the extended service to be changed dynamically, and lastly unsets the profiles field in these services so they do in fact run.

How Has This Been Tested?

I tested both with and without these envs and confirmed all immich services run, that these special services don't run, and that the envs affect building and configuration.

[mmomjian]

Wow, this might be as cursed as my anchors yaml experiment ;)

[mertalev]

lol it's arguably more cursed - I did it this way because anchors weren't powerful enough

[mertalev]

On further discussion with the team, the conclusion is that the convenience of this change is outweighed by the complexity and "magic" it adds to the Compose file.

A better alternative is to develop a script that outputs a more tailored file. This can possibly have a UI in the docs so users can configure the Compose and .env files before downloading them. This obviates the need for the hwaccel files and modifying the Compose file, and can make other features like mounting external libraries less error-prone. It would also accomplish this with a clean and minimal Compose file without any unnecessary clutter.