Add container.FilterSlice function (#30339)

Many places have the following logic:
```go
func (jobs ActionJobList) GetRunIDs() []int64 {
	ids := make(container.Set[int64], len(jobs))
	for _, j := range jobs {
		if j.RunID == 0 {
			continue
		}
		ids.Add(j.RunID)
	}
	return ids.Values()
}
```

this introduces a `container.FilterMapUnique` function, which reduces
the code above to:
```go
func (jobs ActionJobList) GetRunIDs() []int64 {
	return container.FilterMapUnique(jobs, func(j *ActionRunJob) (int64, bool) {
		return j.RunID, j.RunID != 0
	})
}
```

models/issues/review_list.go

@@ -38,12 +38,11 @@ func (reviews ReviewList) LoadReviewers(ctx context.Context) error {
 }
 
 func (reviews ReviewList) LoadIssues(ctx context.Context) error {
-	issueIDs := container.Set[int64]{}
-	for i := 0; i < len(reviews); i++ {
-		issueIDs.Add(reviews[i].IssueID)
-	}
+	issueIDs := container.FilterSlice(reviews, func(review *Review) (int64, bool) {
+		return review.IssueID, true
+	})
 
-	issues, err := GetIssuesByIDs(ctx, issueIDs.Values())
+	issues, err := GetIssuesByIDs(ctx, issueIDs)
 	if err != nil {
 		return err
 	}