*: fix the issue that loadcluster does not remove overlap regions(#2022) (#2039)

[sre-bot]

cherry-pick #2039 to release-3.0

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

What problem does this PR solve?

cherry-pick #2022

What is changed and how it works?

cherry-pick.

Check List

Tests

• Unit test

[nolouch]

/run-all-tests

[codecov-io]

Codecov Report

Merging #2040 into release-3.0 will increase coverage by 0.23%.
The diff coverage is 91.17%.

@@               Coverage Diff               @@
##           release-3.0    #2040      +/-   ##
===============================================
+ Coverage        69.43%   69.67%   +0.23%     
===============================================
  Files              170      170              
  Lines            16769    16787      +18     
===============================================
+ Hits             11644    11696      +52     
+ Misses            4145     4122      -23     
+ Partials           980      969      -11

Impacted Files	Coverage Δ
server/handler.go	51.87% <ø> (+0.25%)	⬆️
server/core/errors.go	62.5% <100%> (+12.5%)	⬆️
server/core/region_kv.go	82.95% <100%> (+1.13%)	⬆️
server/core/kv.go	77.53% <100%> (+1.44%)	⬆️
server/core/region.go	93.5% <100%> (+0.02%)	⬆️
server/core/basic_cluster.go	93.1% <83.33%> (-2.55%)	⬇️
server/cluster_info.go	88.07% <92.3%> (+0.09%)	⬆️
pkg/tempurl/tempurl.go	57.14% <0%> (-14.29%)	⬇️
server/grpc_service.go	58.63% <0%> (+0.42%)	⬆️
... and 8 more

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[nolouch]

/merge

[sre-bot]

/run-all-tests