feat(api): enhance Actions Secrets Management API for repository (#30656)

- Add endpoint to list repository action secrets in API routes
- Implement `ListActionsSecrets` function to retrieve action secrets
from the database
- Update Swagger documentation to include the new
`/repos/{owner}/{repo}/actions/secrets` endpoint
- Add `actions` package import and define new routes for actions,
secrets, variables, and runners in `api.go`.
- Refactor action-related API functions into `Action` struct methods in
`org/action.go` and `repo/action.go`.
- Remove `actionAPI` struct and related functions, replacing them with
`NewAction()` calls.
- Rename `variables.go` to `action.go` in `org` directory.
- Delete `runners.go` and `secrets.go` in both `org` and `repo`
directories, consolidating their content into `action.go`.
- Update copyright year and add new imports in `org/action.go`.
- Implement `API` interface in `services/actions/interface.go` for
action-related methods.
- Remove individual action-related functions and replace them with
methods on the `Action` struct in `repo/action.go`.

---------

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Signed-off-by: appleboy <appleboy.tw@gmail.com>
(cherry picked from commit 852547d0dc70299589c7bf8d00ea462ed709b8e5)

Conflicts:
	routers/api/v1/api.go
	trivial conflict because of Fix #2512 /api/forgejo/v1/version auth check (#2582)

tests/integration/api_repo_secrets_test.go

@@ -24,6 +24,12 @@ func TestAPIRepoSecrets(t *testing.T) {
 	session := loginUser(t, user.Name)
 	token := getTokenForLoggedInUser(t, session, auth_model.AccessTokenScopeWriteRepository)
 
+	t.Run("List", func(t *testing.T) {
+		req := NewRequest(t, "GET", fmt.Sprintf("/api/v1/repos/%s/actions/secrets", repo.FullName())).
+			AddTokenAuth(token)
+		MakeRequest(t, req, http.StatusOK)
+	})
+
 	t.Run("Create", func(t *testing.T) {
 		cases := []struct {
 			Name           string
@@ -31,7 +37,7 @@ func TestAPIRepoSecrets(t *testing.T) {
 		}{
 			{
 				Name:           "",
-				ExpectedStatus: http.StatusNotFound,
+				ExpectedStatus: http.StatusMethodNotAllowed,
 			},
 			{
 				Name:           "-",