add scale command

[glours]

What I did
Add a scale command

Related issue
https://docker.atlassian.net/browse/ENV-310
#10965

(not mandatory) A picture of a cute animal, if possible in relation to what you did

[codecov]

Codecov Report

Patch coverage: 68.57% and project coverage change: +0.17% 🎉

Comparison is base (1311546) 57.72% compared to head (05a6da0) 57.90%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10979      +/-   ##
==========================================
+ Coverage   57.72%   57.90%   +0.17%     
==========================================
  Files         127      129       +2     
  Lines       11092    11160      +68     
==========================================
+ Hits         6403     6462      +59     
- Misses       4058     4060       +2     
- Partials      631      638       +7     

Files Changed	Coverage Δ
pkg/api/api.go	28.84% <ø> (ø)
pkg/api/proxy.go	39.51% <50.00%> (+0.31%)	⬆️
pkg/compose/compose.go	61.32% <50.00%> (ø)
pkg/compose/scale.go	57.14% <57.14%> (ø)
cmd/compose/scale.go	72.22% <72.22%> (ø)
cmd/compose/compose.go	67.92% <100.00%> (+0.08%)	⬆️

... and 5 files with indirect coverage changes

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[ndeloof]

scale used to be a docker-compose v1 command, so I don't think we need this to be introduced as an alpha command, just resurrect the legacy one

$ docker-compose-v1 scale --help
Set number of containers to run for a service.

Numbers are specified in the form `service=num` as arguments.
For example:

    $ docker-compose scale web=2 worker=3

[milas]

Noting that we should update docs after merging this: https://docs.docker.com/compose/migrate/#unsupported-in-v2

The following were deprecated in Compose V1 and aren't supported in Compose V2:

• docker-compose scale. Use docker compose up --scale instead.

[milas]

LGTM

[glours]

Ok my test assertions are fragiles as we can't bet which container will be removed 😬

scale_test.go:54: Running command: docker compose --project-directory fixtures/scale scale dbadmin=1
    scale_test.go:55: assertion failed: expression is false: strings.Contains(res.Combined(), "Container scale-basic-tests-dbadmin-1  Running"):  Container scale-basic-tests-dbadmin-2  Running

I'll improve this tomorrow

[milas]

I'm surprised your assertion failed...I thought we'd made scale deterministic at some point, so that it would always leave the "oldest" (lowest-numbered) replicas

[glours]

@milas I think the 2 replicas were created at the same time 🤷‍♂️
Anyway it's fix now and assertions are way more robust!