perf: speed up job setup, action preparation and the cache server (#1327)

- Look up containers by name instead of listing all of them
- On Linux, cache the docker proxy discovery instead of starting a probe container per job
- Download a job's actions concurrently and share identical fetches between concurrent jobs
- Cache `runner.arch` per run and poll service health every 250ms
- Cache server: queue on an in-process lock instead of polling the database file lock, upload S3 objects up to 64MiB in one request and larger ones in 4 concurrent parts

| `exec`, median of 5 | Before | After |
|---|---:|---:|
| 1 step | 1.70s | 0.87s |
| 10 steps | 2.84s | 1.97s |
| Service + step | 3.78s | 2.18s |
| checkout + Node action | 3.64s | 2.52s |

Reviewed-on: https://gitea.com/gitea/runner/pulls/1327
Reviewed-by: Zettat123 <[email protected]>

internal/app/run/runner_test.go

@@ -156,6 +156,8 @@ func TestRunnerReclaimsVolumesAfterReporting(t *testing.T) {
 						removed.Add(1)
 					}
 					writer.WriteHeader(http.StatusNoContent)
+				case strings.HasPrefix(path, "/containers/") && strings.HasSuffix(path, "/json"):
+					http.NotFound(writer, request)
 				default:
 					t.Errorf("unexpected Docker request: %s %s", request.Method, request.URL)
 					http.NotFound(writer, request)