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/actions/schedule_spec_list.go

@@ -16,11 +16,9 @@ import (
 type SpecList []*ActionScheduleSpec
 
 func (specs SpecList) GetScheduleIDs() []int64 {
-	ids := make(container.Set[int64], len(specs))
-	for _, spec := range specs {
-		ids.Add(spec.ScheduleID)
-	}
-	return ids.Values()
+	return container.FilterSlice(specs, func(spec *ActionScheduleSpec) (int64, bool) {
+		return spec.ScheduleID, true
+	})
 }
 
 func (specs SpecList) LoadSchedules(ctx context.Context) error {
@@ -46,11 +44,9 @@ func (specs SpecList) LoadSchedules(ctx context.Context) error {
 }
 
 func (specs SpecList) GetRepoIDs() []int64 {
-	ids := make(container.Set[int64], len(specs))
-	for _, spec := range specs {
-		ids.Add(spec.RepoID)
-	}
-	return ids.Values()
+	return container.FilterSlice(specs, func(spec *ActionScheduleSpec) (int64, bool) {
+		return spec.RepoID, true
+	})
 }
 
 func (specs SpecList) LoadRepos(ctx context.Context) error {