Support configuration variables on Gitea Actions (#24724)

Co-Author: @silverwind @wxiaoguang 
Replace: #24404

See:
- [defining configuration variables for multiple
workflows](https://docs.github.com/en/actions/learn-github-actions/variables#defining-configuration-variables-for-multiple-workflows)
- [vars
context](https://docs.github.com/en/actions/learn-github-actions/contexts#vars-context)

Related to:
- [x] protocol: https://gitea.com/gitea/actions-proto-def/pulls/7
- [x] act_runner: https://gitea.com/gitea/act_runner/pulls/157
- [x] act: https://gitea.com/gitea/act/pulls/43

#### Screenshoot
Create Variable:

![image](https://user-images.githubusercontent.com/33891828/236758288-032b7f64-44e7-48ea-b07d-de8b8b0e3729.png)


![image](https://user-images.githubusercontent.com/33891828/236758174-5203f64c-1d0e-4737-a5b0-62061dee86f8.png)

Workflow:
```yaml
  test_vars:
    runs-on: ubuntu-latest
    steps:
      - name: Print Custom Variables
        run: echo "${{ vars.test_key }}"
      - name: Try to print a non-exist var
        run: echo "${{ vars.NON_EXIST_VAR }}"
```

Actions Log:

![image](https://user-images.githubusercontent.com/33891828/236759075-af0c5950-368d-4758-a8ac-47a96e43b6e2.png)

---
This PR just implement the org / user (depends on the owner of the
current repository) and repo level variables, The Environment level
variables have not been implemented.
Because
[Environment](https://docs.github.com/en/actions/deployment/targeting-different-environments/using-environments-for-deployment#about-environments)
is a module separate from `Actions`. Maybe it would be better to create
a new PR to do it.

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

routers/api/actions/runner/utils.go

@@ -36,6 +36,7 @@ func pickTask(ctx context.Context, runner *actions_model.ActionRunner) (*runnerv
 		WorkflowPayload: t.Job.WorkflowPayload,
 		Context:         generateTaskContext(t),
 		Secrets:         getSecretsOfTask(ctx, t),
+		Vars:            getVariablesOfTask(ctx, t),
 	}
 
 	if needs, err := findTaskNeeds(ctx, t); err != nil {
@@ -88,6 +89,29 @@ func getSecretsOfTask(ctx context.Context, task *actions_model.ActionTask) map[s
 	return secrets
 }
 
+func getVariablesOfTask(ctx context.Context, task *actions_model.ActionTask) map[string]string {
+	variables := map[string]string{}
+
+	// Org / User level
+	ownerVariables, err := actions_model.FindVariables(ctx, actions_model.FindVariablesOpts{OwnerID: task.Job.Run.Repo.OwnerID})
+	if err != nil {
+		log.Error("find variables of org: %d, error: %v", task.Job.Run.Repo.OwnerID, err)
+	}
+
+	// Repo level
+	repoVariables, err := actions_model.FindVariables(ctx, actions_model.FindVariablesOpts{RepoID: task.Job.Run.RepoID})
+	if err != nil {
+		log.Error("find variables of repo: %d, error: %v", task.Job.Run.RepoID, err)
+	}
+
+	// Level precedence: Repo > Org / User
+	for _, v := range append(ownerVariables, repoVariables...) {
+		variables[v.Name] = v.Data
+	}
+
+	return variables
+}
+
 func generateTaskContext(t *actions_model.ActionTask) *structpb.Struct {
 	event := map[string]interface{}{}
 	_ = json.Unmarshal([]byte(t.Job.Run.EventPayload), &event)