metrics: replace delta with rate

[bufferflies]

Signed-off-by: bufferflies 1045931706@qq.com

What problem does this PR solve?

scheduler some metrics using delta is not correct.
delta: return the last element - the first element in time zone ,so it could not express the ops
rate: return the average increase rate in the time zone

What is changed and how it works?

replace delta with rate

Check List

Tests

Code changes

Side effects

Related changes

• Need to cherry-pick to the release branch

Release note

replace delta with rate in scheduler panel

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• nolouch
• rleungx

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[codecov]

Codecov Report

Merging #4015 (5ac58a6) into master (4a5a745) will increase coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4015      +/-   ##
==========================================
+ Coverage   74.49%   74.61%   +0.12%     
==========================================
  Files         256      256              
  Lines       25827    25827              
==========================================
+ Hits        19239    19272      +33     
+ Misses       4866     4844      -22     
+ Partials     1722     1711      -11     

Flag	Coverage Δ
unittests	74.61% <ø> (+0.12%)	⬆️

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

Impacted Files	Coverage Δ
server/region_syncer/client.go	77.46% <0.00%> (-4.23%)	⬇️
server/statistics/hot_cache_task.go	75.00% <0.00%> (-4.17%)	⬇️
pkg/etcdutil/etcdutil.go	84.70% <0.00%> (-3.53%)	⬇️
server/server.go	72.03% <0.00%> (+0.15%)	⬆️
server/grpc_service.go	47.45% <0.00%> (+0.22%)	⬆️
server/member/member.go	65.24% <0.00%> (+0.53%)	⬆️
server/tso/allocator_manager.go	67.77% <0.00%> (+0.83%)	⬆️
pkg/btree/btree.go	86.74% <0.00%> (+0.96%)	⬆️
server/schedule/operator/step.go	69.76% <0.00%> (+1.66%)	⬆️
server/kv/etcd_kv.go	72.46% <0.00%> (+2.89%)	⬆️
... and 3 more

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[JmPotato]

Are there any screenshots of Grafana that show the actual effect?

[rleungx]

Please change the title to metrics: replace delta with rate

[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: 1760ad4