[to #788] Reduce the number of ObjectMapper creations to improve performance

[Hisoka-X]

What problem does this PR solve?

Problem Description: ObjectMapper is actually a thread-safe object that can be reused to improve performance. Creating an ObjectMapper object is not fast.

What is changed and how does it work?

Code Refactor.

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has methods of interface change
• Has persistent data change
• No code

Check List for Tests

This PR has been tested by at least one of the following methods:

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Possible performance regression, WHY: TBD
• Increased code complexity, WHY: TBD
• Breaking backward compatibility, WHY: TBD
• NO side effects

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation
• Need to be included in the release note
• NO related changes

[ti-chi-bot]

Welcome @Hisoka-X! It looks like this is your first PR to tikv/client-java 🎉

[Hisoka-X]

kindly ping @iosmanthus

[iosmanthus]

@Hisoka-X Thanks for your contribution. 👍