Require approval to run actions for fork pull request (#22803)

Currently, Gitea will run actions automatically which are triggered by
fork pull request. It's a security risk, people can create a PR and
modify the workflow yamls to execute a malicious script.

So we should require approval for first-time contributors, which is the
default strategy of a public repo on GitHub, see [Approving workflow
runs from public
forks](https://docs.github.com/en/actions/managing-workflow-runs/approving-workflow-runs-from-public-forks).

Current strategy:

- don't need approval if it's not a fork PR;
- always need approval if the user is restricted;
- don't need approval if the user can write;
- don't need approval if the user has been approved before;
- otherwise, need approval.

https://user-images.githubusercontent.com/9418365/217207121-badf50a8-826c-4425-bef1-d82d1979bc81.mov

GitHub has an option for that, you can see that at
`/<owner>/<repo>/settings/actions`, and we can support that later.

<img width="835" alt="image"
src="https://user-images.githubusercontent.com/9418365/217199990-2967e68b-e693-4e59-8186-ab33a1314a16.png">

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/actions/status.go

@@ -82,6 +82,10 @@ func (s Status) IsRunning() bool {
 	return s == StatusRunning
 }
 
+func (s Status) IsBlocked() bool {
+	return s == StatusBlocked
+}
+
 // In returns whether s is one of the given statuses
 func (s Status) In(statuses ...Status) bool {
 	for _, v := range statuses {