Implement actions artifacts (#22738)

Implement action artifacts server api.

This change is used for supporting
https://github.com/actions/upload-artifact and
https://github.com/actions/download-artifact in gitea actions. It can
run sample workflow from doc
https://docs.github.com/en/actions/using-workflows/storing-workflow-data-as-artifacts.
The api design is inspired by
https://github.com/nektos/act/blob/master/pkg/artifacts/server.go and
includes some changes from gitea internal structs and methods.

Actions artifacts contains two parts:

- Gitea server api and storage (this pr implement basic design without
some complex cases supports)
- Runner communicate with gitea server api (in comming)

Old pr https://github.com/go-gitea/gitea/pull/22345 is outdated after
actions merged. I create new pr from main branch.


![897f7694-3e0f-4f7c-bb4b-9936624ead45](https://user-images.githubusercontent.com/2142787/219382371-eb3cf810-e4e0-456b-a8ff-aecc2b1a1032.jpeg)

Add artifacts list in actions workflow page.

routers/init.go

@@ -193,6 +193,12 @@ func NormalRoutes(ctx context.Context) *web.Route {
 	if setting.Actions.Enabled {
 		prefix := "/api/actions"
 		r.Mount(prefix, actions_router.Routes(ctx, prefix))
+
+		// TODO: Pipeline api used for runner internal communication with gitea server. but only artifact is used for now.
+		// In Github, it uses ACTIONS_RUNTIME_URL=https://pipelines.actions.githubusercontent.com/fLgcSHkPGySXeIFrg8W8OBSfeg3b5Fls1A1CwX566g8PayEGlg/
+		// TODO: this prefix should be generated with a token string with runner ?
+		prefix = "/api/actions_pipeline"
+		r.Mount(prefix, actions_router.ArtifactsRoutes(ctx, prefix))
 	}
 
 	return r