feat: wait for healthy services and fill the job context (#1107)

Service containers were started and then left alone, so a job's first step could run while a database was still starting up. The runner now waits for every service whose image or `options` declare a healthcheck, as GitHub does. An unhealthy service fails the job with its container log, one that never becomes healthy fails it after `container.service_ready_timeout` (default `5m`, negative disables the wait), and one that exits without a healthcheck only gets its log and a warning.

The started containers also fill the `job` context, whose fields existed but were never populated: `job.container.{id,network}` and `job.services.<id>.{id,network,ports}`. `ports` is keyed by the plain container port, so `job.services.postgres.ports['5432']` resolves to the host port Docker picked.

---------

Co-authored-by: silverwind <me@silverwind.io>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1107
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>
Co-authored-by: bircni <bircni@icloud.com>

act/model/job_context.go

@@ -5,12 +5,18 @@
 package model
 
 type JobContext struct {
-	Status    string `json:"status"`
-	Container struct {
-		ID      string `json:"id"`
-		Network string `json:"network"`
-	} `json:"container"`
-	Services map[string]struct {
-		ID string `json:"id"`
-	} `json:"services"`
+	Status    string                `json:"status"`
+	Container JobContainerContext   `json:"container"`
+	Services  map[string]JobService `json:"services"`
+}
+
+type JobContainerContext struct {
+	ID      string `json:"id"`
+	Network string `json:"network"`
+}
+
+type JobService struct {
+	ID      string            `json:"id"`
+	Network string            `json:"network"`
+	Ports   map[string]string `json:"ports"` // container port to the published host port
 }