split_controller : split region based on hot keys and print key info

[mittalrishabh]

What is changed and how it works?

Issue Number: Close #xxx

What's Changed:
It is splitting the range based on hot keys and printing the region keys in the message

Related changes

• PR to update pingcap/docs/pingcap/docs-cn:
• Need to cherry-pick to the release branch

Check List

Tests

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

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Release note

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This cherry pick PR is for a release branch and has not yet been approved by triage owners.
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Hi @mittalrishabh. Thanks for your PR.

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[JmPotato]

One risk of doing this is that, due to one less sampling, the final number of regions to be split may increase. In this case, when a hotspot appears, increasing the number of regions may bring additional side effects, such as increasing the number of tasks or gRPC poll times, thereby affecting performance. We should conduct some tests on this change before merging it.

[mittalrishabh]

ok, i raised this github PR #17010 only for logging. Let me know how it looks.

[mittalrishabh]

Why are you using the hottest key range inside top_cpu_usage(). Shouldn't we do sampling over there.