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>

options/locale/locale_en-US.ini

@@ -132,6 +132,9 @@ show_full_screen = Show full screen
 
 confirm_delete_selected = Confirm to delete all selected items?
 
+name = Name
+value = Value
+
 [aria]
 navbar = Navigation Bar
 footer = Footer
@@ -3391,8 +3394,6 @@ owner.settings.chef.keypair.description = Generate a key pair used to authentica
 secrets = Secrets
 description = Secrets will be passed to certain actions and cannot be read otherwise.
 none = There are no secrets yet.
-value = Value
-name = Name
 creation = Add Secret
 creation.name_placeholder = case-insensitive, alphanumeric characters or underscores only, cannot start with GITEA_ or GITHUB_
 creation.value_placeholder = Input any content. Whitespace at the start and end will be omitted.
@@ -3462,6 +3463,22 @@ runs.no_matching_runner_helper = No matching runner: %s
 
 need_approval_desc = Need approval to run workflows for fork pull request.
 
+variables = Variables
+variables.management = Variables Management
+variables.creation = Add Variable
+variables.none = There are no variables yet.
+variables.deletion = Remove variable
+variables.deletion.description = Removing a variable is permanent and cannot be undone. Continue?
+variables.description = Variables will be passed to certain actions and cannot be read otherwise.
+variables.id_not_exist = Variable with id %d not exists.
+variables.edit = Edit Variable
+variables.deletion.failed = Failed to remove variable.
+variables.deletion.success = The variable has been removed.
+variables.creation.failed = Failed to add variable.
+variables.creation.success = The variable "%s" has been added.
+variables.update.failed = Failed to edit variable.
+variables.update.success = The variable has been edited.
+
 [projects]
 type-1.display_name = Individual Project
 type-2.display_name = Repository Project