github/workflows: always use latest stable docker compose release

docker compose v2.36.2 introduced a regression [1] making labgrid's
docker image generation fail:

  Container staging-dut-1  Creating
  Container staging-coordinator-1  Creating
  Container staging-dut-1  Error response from daemon: No such image: staging-dut:latest
  Error response from daemon: No such image: staging-dut:latest
  Error: Process completed with exit code 1.

The issue has been resolved for nearly a month, but there is still no
GitHub runner image [2] that includes it. It is recommended [3] to use
docker's official setup-compose-action to benefit from stable releases
as early as possible [4]:

  If Docker Compose is already installed on the runner, the action will
  skip download. Otherwise, it will download and install the latest
  stable version available on GitHub.

[1] docker/compose#12896
[2] https://github.com/actions/runner-images/releases
[3] docker/compose#12892 (comment)
[4] https://github.com/docker/setup-compose-action

Signed-off-by: Bastian Krause <bst@pengutronix.de>
(cherry picked from commit 84c494b)

Author: Bastian-Krause

.github/workflows/docker.yml

@@ -19,6 +19,9 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
     - uses: actions/checkout@v4
+    - uses: docker/setup-compose-action@v1
+      with:
+        version: latest
     - name: Install system dependencies
       run: |
         sudo apt install -yq python3-pip python3-setuptools-scm

.github/workflows/reusable-unit-tests-docker.yml

@@ -14,6 +14,9 @@ jobs:
     - uses: actions/checkout@v4
       with:
         ref: ${{ inputs.branch }}
+    - uses: docker/setup-compose-action@v1
+      with:
+        version: latest
     - name: Install system dependencies
       run: |
         sudo apt install -yq python3-pip python3-setuptools-scm