rules: optimize the implementation of FitRegion

[HunDunDM]

Signed-off-by: HunDunDM hundundm@gmail.com

What problem does this PR solve?

// FitRegion tries to fit the region with placement rules.
func (c *RaftCluster) FitRegion(region *core.RegionInfo) *placement.RegionFit {
	return c.GetRuleManager().FitRegion(c, region)
}

Due to the above code, CacheCluster in #4003 has no real effect. It is called RaftCluster.GetStores, not CacheCluster.GetStores.

What is changed and how it works?

Implementation of abstract FitRegion.

Check List

Tests

• Unit test

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

None

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• bufferflies
• disksing

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[codecov]

Codecov Report

Merging #4012 (97fe20a) into master (08f92d6) will increase coverage by 0.07%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4012      +/-   ##
==========================================
+ Coverage   74.46%   74.54%   +0.07%     
==========================================
  Files         258      258              
  Lines       26323    26322       -1     
==========================================
+ Hits        19601    19621      +20     
+ Misses       4975     4962      -13     
+ Partials     1747     1739       -8     

Flag	Coverage Δ
unittests	74.54% <100.00%> (+0.07%)	⬆️

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

Impacted Files	Coverage Δ
pkg/mock/mockcluster/mockcluster.go	95.22% <ø> (-0.02%)	⬇️
server/cluster/cluster.go	83.03% <ø> (+0.80%)	⬆️
server/schedule/checker/priority_checker.go	78.94% <100.00%> (ø)
server/schedule/checker/rule_checker.go	82.88% <100.00%> (ø)
server/schedule/filter/filters.go	90.69% <100.00%> (ø)
server/schedule/operator/builder.go	88.39% <100.00%> (ø)
server/schedule/opt/healthy.go	100.00% <100.00%> (ø)
server/schedule/opt/opts.go	100.00% <100.00%> (ø)
server/schedulers/shuffle_hot_region.go	55.55% <0.00%> (-10.11%)	⬇️
server/member/member.go	63.10% <0.00%> (-3.21%)	⬇️
... and 15 more

---

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[bufferflies]

lgtm

[nolouch]

/merge

[ti-chi-bot]

@nolouch: It seems you want to merge this PR, I will help you trigger all the tests:

/run-all-tests

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[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: cbe775b