[Bug] Update logic on CheckpointState around serialization/deserialization

[dreamer-89]

Description

As part of #5282, we introduced a boolean flag in CheckpointState inside ReplicationTracker with incorrect serialization/deserialization logic.

The bwc tests (using on CheckpointState for transport communication e.g. RecoveryHandoffPrimaryContextRequest) fails on 2.x because of in.getVersion().onOrAfter(Version.CURRENT) (2.5.0) < Version.Current (2.6.0); resulting in else block execution thereby skipping read on boolean. BUT, the write to outputstream is unconditional which means the minor version (2.5.0 containing #5282 change) writes to output stream.

The correct fix here is:

1. Replace Version.CURRENT with specific version. Version.CURRENT is unreliable as it changes with branch and difficult to argue about in code
2. Update output stream write to be conditional so that it writes only when it is supported.

if (in.getVersion().onOrAfter(Version.V_2_5_0)) {
    this.replicated = in.readBoolean();
} else {
    this.replicated = true;
}

Issues Resolved

#5801
#5766

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff
• Commit changes are listed out in CHANGELOG.md file (See: Changelog)

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[github-actions]

Gradle Check (Jenkins) Run Completed with:

• RESULT: SUCCESS ✅
• URL: https://build.ci.opensearch.org/job/gradle-check/9235/
• CommitID: 39822b1