feat: support both local and global ratelimit simultaneously

[kkk777-7]

What this PR does / why we need it:
Support both local and global ratelimit in BackendTrafficPolicy simultaneously.
Requests are evaluated first by the local limit, then by the global limit.

Which issue(s) this PR fixes:

Fixes #7271

Release Notes: Yes

[codecov]

Codecov Report

❌ Patch coverage is 82.75862% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.38%. Comparing base (d4e44fd) to head (3ed043e).

Files with missing lines	Patch %	Lines
internal/gatewayapi/backendtrafficpolicy.go	82.14%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7334      +/-   ##
==========================================
+ Coverage   72.34%   72.38%   +0.03%     
==========================================
  Files         231      231              
  Lines       33896    33918      +22     
==========================================
+ Hits        24521    24550      +29     
+ Misses       7614     7607       -7     
  Partials     1761     1761              

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[arkodg]

imo not needed, since these are applied to different filters, prefer minimal changes to enable this

[kkk777-7]

thanks, I misunderstood 🙏 I’ve reverted it.

[arkodg]

Is this needed

[kkk777-7]

maybe, append operation is necessary to avoid overwriting the local rate limit config.
https://github.com/envoyproxy/gateway/blob/main/internal/xds/translator/local_ratelimit.go#L139

[arkodg]

is this an existing bug or related to this PR ?
cc @zhaohuabing

[kkk777-7]

this is related to this PR.
I believe there was no issue before because we had only used either local or global, not both.

[arkodg]

the code flow for local looks like its different

gateway/internal/xds/translator/local_ratelimit.go

Line 138 in cb8a7ca

rateLimits, descriptors := buildRouteLocalRateLimits(local)

vs global

gateway/internal/xds/translator/ratelimit.go

Line 212 in cb8a7ca

global := route.Traffic.RateLimit.Global

[kkk777-7]

avoid overwriting the local rate limit config.

sorry, my word make mislead.

There’s no issue converting both the local and global configurations from irRoute to routev3.RateLimit.
However, since both converted routev3.RateLimit are set on the same xdsRouteAction, if we don’t append them, only the later processed (global) routev3.RateLimit will take effect.

[arkodg]

ah in that case, we need to bring back the local_ prefix to ensure uniqueness in descriptors, my bad