fix: avoid 'filename too long' on matrix jobs by hashing container names (#853)

## Bug fixes

- Fixed "file name too long" errors when running matrix jobs with many or
  long-valued matrix parameters. Docker volume and container names are now
  bounded to a safe length by hashing the full name with SHA-256, keeping
  the result well within the filesystem `NAME_MAX` limit (255 bytes) even
  after Docker appends its own suffixes (`-env`, `-network`, etc.).

## Upgrade notes

This change renames the Docker containers, volumes and networks created by
the runner. Resources created by a previous version will **not** be cleaned
up automatically after upgrade and will become orphans.

After upgrading, you can remove the legacy resources with:

```sh
# volumes
docker volume ls -q | grep -E '^GITEA-ACTIONS-TASK-[0-9]+_' | xargs -r docker volume rm

# networks
docker network ls --format '{{.Name}}' | grep -E '^GITEA-ACTIONS-TASK-[0-9]+_.*-network$' | xargs -r docker network rm
```

> **Note:** If multiple act_runner instances share the same Docker daemon,
> make sure no runner using the old version is running before executing the
> cleanup commands above.

Fixes #686

---------

Co-authored-by: Nicolas <[email protected]>
Reviewed-on: https://gitea.com/gitea/act_runner/pulls/853
Reviewed-by: silverwind <[email protected]>
Co-authored-by: Morgan Peyre <[email protected]>
Co-committed-by: Morgan Peyre <[email protected]>

act/runner/step_docker.go

@@ -127,7 +127,7 @@ func (sd *stepDocker) newStepContainer(ctx context.Context, image string, cmd, e
 		Image:        image,
 		Username:     rc.Config.Secrets["DOCKER_USERNAME"],
 		Password:     rc.Config.Secrets["DOCKER_PASSWORD"],
-		Name:         createSimpleContainerName(rc.jobContainerName(), "STEP-"+step.ID),
+		Name:         createContainerName(rc.jobContainerName(), "STEP-"+step.ID),
 		Env:          envList,
 		Mounts:       mounts,
 		NetworkMode:  networkMode,