[improvement](scan) merge scan keys based on the number of scanners

[mrhhsg]

Proposed changes

Issue Number: close #xxx

Problem Summary

A scanner that takes too many scan keys will cause performance degradation, so it's better to try to merge the scan keys.

Describe your changes.

Checklist(Required)

1. Does it affect the original behavior:
   • [ ] Yes
   • [x] No
   • [ ] I don't know
2. Has unit tests been added:
   • [ ] Yes
   • [x] No
   • [ ] No Need
3. Has document been added or modified:
   • [ ] Yes
   • [x] No
   • [ ] No Need
4. Does it need to update dependencies:
   • [ ] Yes
   • [x] No
5. Are there any changes that cannot be rolled back:
   • [ ] Yes (If Yes, please explain WHY)
   • [x] No

Further comments

If this is a relatively large or complex change, kick off the discussion at [email protected] by explaining why you chose the solution you did and what alternatives you considered, etc...