Handle the incorrect milestone of MRs

In #22 (closed), we use "schedules" to fill the milestone of the merged MR, it will execute daily and will check for MRs that have no milestones in the past month.

In this issue, we also need to handle the incorrect milestone of MRs.

Handle type

Use triage reactive processor to handle this, when mr is merged, immediately correct his milestones.

Correct logic

We can refer to #22 (closed), use two times(merged time and release branch time) to determine the correct milestone of the MR.