pkg: improve region path

[rleungx]

What problem does this PR solve?

Issue Number: Ref #7897.

What is changed and how does it work?

$ benchstat old.txt new.txt
goos: linux
goarch: amd64
pkg: github.com/tikv/pd/pkg/storage/endpoint
cpu: Intel(R) Xeon(R) Gold 6240 CPU @ 2.60GHz
              │   old.txt    │               new.txt               │
              │    sec/op    │   sec/op     vs base                │
RegionPath-72   132.70n ± 2%   97.37n ± 4%  -26.62% (p=0.000 n=10)

              │  old.txt   │              new.txt               │
              │    B/op    │    B/op     vs base                │
RegionPath-72   48.00 ± 0%   39.00 ± 0%  -18.75% (p=0.000 n=10)

              │  old.txt   │              new.txt               │
              │ allocs/op  │ allocs/op   vs base                │
RegionPath-72   2.000 ± 0%   1.000 ± 0%  -50.00% (p=0.000 n=10)

Check List

Tests

• Unit test

Release note

None.

[ti-chi-bot]

[REVIEW NOTIFICATION]

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• JmPotato
• nolouch

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[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 77.42%. Comparing base (7e85817) to head (ca80c71).

❗ Current head ca80c71 differs from pull request most recent head 4efa522. Consider uploading reports for the commit 4efa522 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8180      +/-   ##
==========================================
+ Coverage   77.38%   77.42%   +0.04%     
==========================================
  Files         471      471              
  Lines       61364    61366       +2     
==========================================
+ Hits        47487    47514      +27     
+ Misses      10313    10290      -23     
+ Partials     3564     3562       -2     

Flag	Coverage Δ
unittests	77.42% <80.00%> (+0.04%)	⬆️

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[nolouch]

/merge

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[ti-chi-bot]

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

Commit hash: ca80c71

[ti-chi-bot]

@rleungx: Your PR was out of date, I have automatically updated it for you.

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