[feature-wip](unique-key-merge-on-write) show enable_unique_key_merge_on_write property when get ddl

[liaoxin01]

Proposed changes

Issue Number: close #xxx

Problem summary

Unique key table show enable_unique_key_merge_on_write property when get ddl statement.

Checklist(Required)

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

[github-actions[bot]]

PR approved by anyone and no changes requested.