fix: honor volumes declared on service containers (#1186)

Service containers were built without a volume policy, so every bind and mount they declared was dropped, whatever `valid_volumes` allowed. GitHub passes a service's declared volumes straight to `docker create`, so a workflow that mounts into a service silently did nothing here. Services now get the configured policy, but not `validVolumes()`, which would also hand them the docker daemon socket that GitHub mounts only into the job container.

### What changes for users

On the default `valid_volumes: []` nothing changes: a service's volumes are still dropped, now with a warning rather than in silence. Once `valid_volumes` is configured, a service's declared volumes are honored under it instead of discarded, which is what that setting already documents. No workflow that worked before stops working, and a service can reach no volume the policy does not already allow the job container, so this is not a breaking change.

---------

Co-authored-by: bircni <bircni@icloud.com>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1186
Reviewed-by: bircni <bircni@icloud.com>
Co-authored-by: silverwind <me@silverwind.io>

act/container/docker_run_test.go

@@ -570,7 +570,7 @@ func TestCheckVolumes(t *testing.T) {
 	}
 	for _, tc := range testCases {
 		t.Run(tc.desc, func(t *testing.T) {
-			logger, _ := test.NewNullLogger()
+			logger, hook := test.NewNullLogger()
 			ctx := common.WithLogger(context.Background(), logger)
 			cr := &containerReference{
 				input: &NewContainerInput{
@@ -579,6 +579,7 @@ func TestCheckVolumes(t *testing.T) {
 			}
 			_, hostConf := cr.sanitizeConfig(ctx, &container.Config{}, &container.HostConfig{Binds: tc.binds})
 			assert.Equal(t, tc.expectedBinds, hostConf.Binds)
+			assert.Len(t, hook.AllEntries(), len(tc.binds)-len(tc.expectedBinds)) // every drop is warned about
 		})
 	}
 }