fix: allow envoyHpa maxReplicas to be equal to minReplicas

[shahar-h]

What this PR does / why we need it:
According to hpa spec maxReplicas cannot be less that minReplicas. The current cel validation also forbids it to be equal to minReplicas.
This PR fixes the validation to be aligned with the spec and also adds a test.

Which issue(s) this PR fixes: N/A

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (d13c329) 64.54% compared to head (8200ff0) 64.50%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2329      +/-   ##
==========================================
- Coverage   64.54%   64.50%   -0.04%     
==========================================
  Files         112      112              
  Lines       15949    15949              
==========================================
- Hits        10294    10288       -6     
- Misses       5007     5013       +6     
  Partials      648      648              

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[zhaohuabing]

I'm curious why K8s allows maxReplicas to be equal to minReplicas.

imo, EG should leave the current validation as it is: maxReplicas must bigger than minReplicas, unless we have a strong reason to change it.

[arkodg]

I would accept this PR to handle one use case - debugging something in EG while having hpa enabled but temporarily keeping the replicas constant, this can be achieved using replicas, but requires the user to delete and readd more config rather than simply editing fields

[zhaohuabing]

I would accept this PR to handle one use case - debugging something in EG while having hpa enabled but temporarily keeping the replicas constant, this can be achieved using replicas, but requires the user to delete and readd more config rather than simply editing fields

Ha, this is a legitimate use case. I guess that's also why k8s allows that.

[zhaohuabing]

LGTM. Thanks!