feat: Clean up the API constants for v4

[jinlinGuan]

Replace constant name "EchoRoute" with original "Route"

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Codecov Report

Attention: Patch coverage is 0% with 26 lines in your changes missing coverage. Please review.

Project coverage is 43.71%. Comparing base (80a711a) to head (bf174a4).

Files with missing lines	Patch %	Lines
clients/interfaces/mocks/AuthenticationInjector.go	0.00%	26 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #965      +/-   ##
==========================================
+ Coverage   43.29%   43.71%   +0.42%     
==========================================
  Files         112      111       -1     
  Lines        6860     6693     -167     
==========================================
- Hits         2970     2926      -44     
+ Misses       3646     3532     -114     
+ Partials      244      235       -9     

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[cloudxxx8]

LGTM