[Improve](report) drop replica by batch prevent be cannot delete replica cased by fe oom

[qzsee]

What problem does this PR solve?

We encountered the following situation:
Doris cluster : 1 fe and 3 be.

1. The user creates a table with about 6000w replicas and each be has about 2000W replicas.
2. Then the user deleted this table
3. fe consumes a lot of memory during each be tablet report. fe needs to iterate over these tablets and issue a drop replica task to be. fe will continue to consume more memory.
4. In this case, fe cannot send a drop replica task to be. As a result, be cannot delete replicas

Therefore, we send drop replica tasks to be in batches

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

None

Check List (For Author)

• Test

  • Regression test
  • Unit Test
  • Manual test (add detailed scripts or steps below)
  • No need to test or manual test. Explain why:
    • This is a refactor/code format and no logic has been changed.
    • Previous test can cover this change.
    • No code files have been changed.
    • Other reason

• Behavior changed:

  • No.
  • Yes.

• Does this need documentation?

  • No.
  • Yes.

Check List (For Reviewer who merge this PR)

• Confirm the release note
• Confirm test cases
• Confirm document
• Add branch pick label

[hello-stephen]

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