schedulers: adjust calculate rank process

[nolouch]

Signed-off-by: nolouch nolouch@gmail.com

What problem does this PR solve?

Fix the problem that read hotspot scheduling cannot converge well.

What is changed and how it works?

• adjust the method of calculate rank process. (SrcStore consider the peer)
• adjust the size of the window of reading statistic

Release note

Fix the problem that read hotspot scheduling cannot converge well.

Check List

Tests

• Unit test
• Manual test (add detailed scripts or steps below)
  
  

[codecov-io]

Codecov Report

Merging #2314 into master will decrease coverage by 0.19%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master    #2314      +/-   ##
==========================================
- Coverage   77.10%   76.91%   -0.20%     
==========================================
  Files         203      203              
  Lines       22277    22249      -28     
==========================================
- Hits        17177    17113      -64     
- Misses       3803     3829      +26     
- Partials     1297     1307      +10     

Impacted Files	Coverage Δ
server/schedulers/hot_region.go	82.39% <66.66%> (-0.10%)	⬇️
server/statistics/store.go	71.01% <100.00%> (ø)
tools/pd-backup/pdbackup/backup.go	0.00% <0.00%> (-39.40%)	⬇️
server/schedulers/shuffle_hot_region.go	63.96% <0.00%> (-9.91%)	⬇️
server/region_syncer/client.go	79.38% <0.00%> (-6.88%)	⬇️
server/heartbeat_streams.go	67.00% <0.00%> (-6.00%)	⬇️
server/schedulers/random_merge.go	61.19% <0.00%> (-2.99%)	⬇️
server/member/leader.go	73.10% <0.00%> (-2.53%)	⬇️
pkg/mock/mockhbstream/mockhbstream.go	89.23% <0.00%> (-1.54%)	⬇️
pkg/etcdutil/etcdutil.go	82.60% <0.00%> (-1.45%)	⬇️
... and 6 more

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[lhy1024]

/merge

[sre-bot]

/run-all-tests

[HunDunDM]

LGTM