tools/simulator: Make simulator work with large scale cluster

[HuSharp]

What problem does this PR solve?

separate regions and heartbeat to make simulator work with large scale cluster

Issue Number: Close #5683, Ref #8135

What is changed and how does it work?

support 300 stores with 1000k regions tiup playground nightly --kv.binpath ./pd-simulator --kv=1 --db=0 --kv.config=../conf/simconfig.toml --pd 1

after adding a node

Check List

Tests

• Manual test (add detailed scripts or steps below)

Release note

None.

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Skipping CI for Draft Pull Request. If you want CI signal for your change, please convert it to an actual PR. You can still manually trigger a test run with /test all

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.29%. Comparing base (41e6376) to head (64f0fad).

:exclamation: Current head 64f0fad differs from pull request most recent head 3553c7d

Please upload reports for the commit 3553c7d to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8269 +/- ## ========================================== + Coverage 77.25% 77.29% +0.03% ========================================== Files 470 470 Lines 61495 61356 -139 ========================================== - Hits 47511 47424 -87 + Misses 10434 10368 -66 - Partials 3550 3564 +14 ``` | [Flag](https://app.codecov.io/gh/tikv/pd/pull/8269/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/tikv/pd/pull/8269/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv) | `77.29% <ø> (+0.03%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tikv#carryforward-flags-in-the-pull-request-comment) to find out more.

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