schedulers: opt balance witness when store nr larger than peer nr

[ethercflow]

ref #5762

What problem does this PR solve?

Issue Number: ref #5762

What is changed and how does it work?

1. When stores nr larger than peers nr, move witness instead of transfer witenss
2. For the same region, when witness switching occurs, the order of step generation is guaranteed: demote witness(peer1) to witness learner, non-witness learner, voter, voter (peer2) -> witness, to avoid there is a non-witness learner applying snapshot and a witness at the same time
3. When verifying the legitimacy of the targetLeader in the builder, the judgment is made based on the result of the transfer witness instead of the intermediate state
4. Add metrics in pd.json
5. Consider witness when statistic regions info

schedulers: opt balance witness when store nr larger than peer nr

Check List

Tests

• Unit test
• Integration test
• Manual test
  • Test with sysbench prepare

Code changes

• None

Side effects

• None

Related changes

• None

Release note

None.

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[codecov]

Codecov Report

Patch coverage: 81.86% and project coverage change: -0.02 ⚠️

Comparison is base (0b36238) 74.41% compared to head (f3b533c) 74.40%.

❗ Current head f3b533c differs from pull request most recent head c4afec6. Consider uploading reports for the commit c4afec6 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6149      +/-   ##
==========================================
- Coverage   74.41%   74.40%   -0.02%     
==========================================
  Files         391      392       +1     
  Lines       38175    38316     +141     
==========================================
+ Hits        28409    28510     +101     
- Misses       7241     7283      +42     
+ Partials     2525     2523       -2     

Flag	Coverage Δ
unittests	74.40% <81.86%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
server/cluster/cluster.go	82.23% <0.00%> (+0.09%)	⬆️
pkg/schedule/operator/step.go	77.10% <61.11%> (-0.16%)	⬇️
pkg/schedule/schedulers/balance_witness.go	65.89% <69.01%> (-1.17%)	⬇️
pkg/schedule/operator/create_operator.go	90.96% <75.00%> (-0.81%)	⬇️
pkg/schedule/operator/builder.go	86.34% <94.44%> (-0.26%)	⬇️
pkg/core/basic_cluster.go	94.33% <100.00%> (+0.58%)	⬆️
pkg/core/region.go	88.97% <100.00%> (ø)
pkg/core/region_tree.go	95.65% <100.00%> (+0.08%)	⬆️
pkg/schedule/schedulers/utils.go	89.93% <100.00%> (+0.25%)	⬆️

... and 37 files with indirect coverage changes

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[bufferflies]

how about add new filter for this store? like excludedFilter.

[ti-chi-bot]

PR needs rebase.

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