*: unify the etcd naming

[rleungx]

What problem does this PR solve?

Issue Number: Ref #4399

What is changed and how does it work?

We should use Etcd instead of ETCD.

Check List

Tests

• Unit test

Release note

None.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 77.33%. Comparing base (5e0fdb8) to head (950adb4).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8496      +/-   ##
==========================================
- Coverage   77.37%   77.33%   -0.04%     
==========================================
  Files         472      472              
  Lines       61796    61796              
==========================================
- Hits        47812    47791      -21     
- Misses      10422    10431       +9     
- Partials     3562     3574      +12     

Flag	Coverage Δ
unittests	77.33% <50.00%> (-0.04%)	⬇️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JmPotato, lhy1024

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2024-08-06 07:28:42.610169222 +0000 UTC m=+337052.477268308: ☑️ agreed by lhy1024.
• 2024-08-06 07:55:05.641805303 +0000 UTC m=+338635.508904391: ☑️ agreed by JmPotato.