schedule/placement/fit: cache the match info for rules to peers

[AndreMouche]

What problem does this PR solve?

Issue Number: Close #5276

Check List

Tests

• Unit test

• benchmark

current branch

➜  placement git:(fit_cache) ✗ go test -benchmem -run=^$ -bench ^BenchmarkFitRegionWithMoreRulesAndStoreLabels -benchtime=100x
goos: darwin
goarch: amd64
pkg: github.com/tikv/pd/server/schedule/placement
cpu: VirtualApple @ 2.50GHz
BenchmarkFitRegionWithMoreRulesAndStoreLabels-8              100           5371767 ns/op          356880 B/op      12879 allocs/op
PASS
ok      github.com/tikv/pd/server/schedule/placement    1.601s

master

➜  placement git:(master) ✗ go test -benchmem -run=^$ -bench ^BenchmarkFitRegionWithMoreRulesAndStoreLabels -benchtime=100x
goos: darwin
goarch: amd64
pkg: github.com/tikv/pd/server/schedule/placement
cpu: VirtualApple @ 2.50GHz
BenchmarkFitRegionWithMoreRulesAndStoreLabels-8              100          47968061 ns/op         2627010 B/op     107788 allocs/op
PASS
ok      github.com/tikv/pd/server/schedule/placement    5.801s

Release note

None.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.81%. Comparing base (f5d4636) to head (2df2a09).
Report is 1548 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5277      +/-   ##
==========================================
+ Coverage   75.70%   75.81%   +0.11%     
==========================================
  Files         311      311              
  Lines       30826    30835       +9     
==========================================
+ Hits        23338    23379      +41     
+ Misses       5485     5464      -21     
+ Partials     2003     1992      -11     

Flag	Coverage Δ
unittests	75.81% <100.00%> (+0.11%)	⬆️

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[ti-chi-bot]

@AndreMouche: PR needs rebase.

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