(storage) Level1Iterator should release iterators in heap

[dataroaring]

When there is a query with limit, e.g. select * from limit 1, scanners are closed by FragmentExecutor, then some scanners do not run to eof and mem leaks happen.

We have to release iterators in the heap.

Proposed changes

Issue Number: close #xxx

Problem summary

Describe your changes.

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

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