fix: bound blocking calls and stop failing silently (#1174)

Jobs occasionally go silent ([example](https://gitea.com/gitea/runner/actions/runs/805045/jobs/1055123)) mid-run and Gitea reaped them after `ZOMBIE_TASK_TIMEOUT`, with no error in the log. This contains a number of related fixes, all with full test coverage:

1. Bound every RPC to Gitea with a timeout, a stalled report otherwise parked logs and heartbeats for the whole job.
2. Cap `runner.fetch_timeout` at that ceiling.
3. Let only the daemon loop close its own channel, the race panicked the process.
4. Stop the job on any terminal server result, not just `RESULT_CANCELLED`.
5. Report that result instead of relabelling it as cancelled.
6. Log reporting failures once at each end of an outage instead of discarding them.
7. Clamp the acknowledged log index, a too-large ack panicked on a slice bound.
8. Stop reading server health from a `FetchTask` deadline, it marked the runner healthy and reset the error backoff on a timeout.
9. Return an error from the Docker version probe instead of a `logrus` panic.
10. Pass the context to go-git's fetch and pull.
11. Fail the clone when a refresh dies on a cancelled context.
12. Set `terminationGracePeriodSeconds` in the Kubernetes examples.

Also contains a deprecation fix for goreleaser.

Reviewed-on: https://gitea.com/gitea/runner/pulls/1174
Reviewed-by: bircni <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>

examples/kubernetes/README.md

@@ -11,6 +11,8 @@ Each example persists **two** things, and it is worth knowing which is which:
 - `/data` is the runner's working directory. It holds the `.runner` registration file and, optionally, the config file — so the runner re-attaches to the server instead of registering again.
 - The Docker daemon's data root holds the images pulled for jobs (`/var/lib/docker` for the dind sidecar, `/home/rootless/.local/share/docker` for `dind-rootless`). It is *not* under `/data`. If you drop this volume, the examples still work, but the image cache is discarded whenever the pod is recreated and every job re-pulls its images.
 
+- Kubernetes SIGKILLs a pod 30s after SIGTERM by default, long before a job finishes and reports its result, which leaves tasks the server can only reap as zombies. The manifests raise `terminationGracePeriodSeconds` to three hours, matching the systemd example and the `runner.timeout` job ceiling; set `runner.shutdown_timeout` below that so the runner drains jobs within the window rather than being killed mid-cleanup.
+
 Files in this directory:
 
 - [`dind-docker.yaml`](dind-docker.yaml)