Switch docker builds in CI to bake

[janbrasna]

If this changeset needs to go into the FXC codebase, please add the WMO and FXC label. 💯

One-line summary

Compose will no longer provide its own builder and bake is the new default. The flag to opt-out will cease to function in some of the next versions.

Significant changes and points to review

Also removes unused builder container spinning up, unused python env, and bumps some actions.

The timeout is increased before a better rerun strategy is in place, as it's been hit a few times recently.

Issue / Bugzilla link

#16464

Testing

(this change will run on this PR also, to show the difference…)

https://github.com/mozilla/bedrock/actions/runs/18161547727/job/51693290418#step:3:2200

#1 [internal] load local bake definitions
#1 reading from stdin 869B done
#1 DONE 0.0s

#2 [app internal] load build definition from Dockerfile
#2 transferring dockerfile: 3.28kB done
#2 DONE 0.0s

Comparing with the previous run at 2m50sec, this took 2m40sec with all the handing off between drivers et al. so luckily it does not appear to be slower at this point.

Also tested some newer compose versions explicitly (that got mentioned in "our" issue) and passing too:

• v2.39.2 /runs/18201932555
• v2.39.4 /runs/18202077817/

┆Issue is synchronized with this Jira Task
┆Priority: P2
┆Sprint: Backlog

[stevejalim]

Integration tests run passed https://github.com/mozilla/bedrock/actions/runs/18588845367

[janbrasna]

This clocks in at ±5:20~ish:

Fri, 17 Oct 2025 09:25:53 GMT #1 [internal] load local bake definitions
[…]
Fri, 17 Oct 2025 09:31:16 GMT #102 DONE 0.0

Which is pretty much same as 5:20 yesterday:

Wed, 15 Oct 2025 16:26:10 GMT #1 [release internal] load build definition from Dockerfile
[…]
Wed, 15 Oct 2025 16:31:30 GMT #87 DONE 0.0s

(Tried looking into the extra length of instructions logged in the test image build, but didn't see anything obvious; context, caches, all look pretty much same in terms of commands/operations performed. Couldn't find any extra verbosity. EDIT: Looking back through more builds they also run into the hundred+ range so it's a matter of layers reused in a given changeset I guess.)