[fix](fe) add compatible code for CloudTablet

[mymeiyi]

What problem does this PR solve?

#59814 modify replicas to replica in CloudTablet, and will merge into 4.1.
This pr add compatible code for CloudTablet to make 4.1 can downgrade to 4.0.

Issue Number: close #xxx

Related PR: #xxx

Problem Summary:

Release note

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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

[Thearas]

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Please clearly describe your PR:

1. What problem was fixed (it's best to include specific error reporting information). How it was fixed.
2. Which behaviors were modified. What was the previous behavior, what is it now, why was it modified, and what possible impacts might there be.
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4. Which code was refactored and why was this part of the code refactored?
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[Copilot]

Pull request overview

This PR adds backward compatibility code to CloudTablet to support downgrading from version 4.1 to 4.0. PR #59814 changed CloudTablet to use a singular replica field instead of the replicas list. This PR introduces a migration mechanism using GsonPostProcessable to convert the old serialization format to the new one during deserialization.

Changes:

• Implements GsonPostProcessable interface in CloudTablet
• Adds a temporary replica field with SerializedName "r" to capture v4.1 serialized data
• Implements gsonPostProcess() method to migrate the singular replica to the replicas list during deserialization

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[dataroaring]

run buildall

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run buildall