Add the ability to set the hits_addend for a given rate_limit request via a hardcoded dynamic metadata field (#34184)

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Commit Message: Adds the ability to set the hits_addend for a given
rate_limit request via a hardcoded dynamic metadata field:
envoy.ratelimit:hits_addend.
Additional Description:
Risk Level: Low
Testing: Added unit test. I have also manually tested this using
gloo-edge as the control-plane.
Docs Changes:
Release Notes:
Platform Specific Features: N/A
[Optional Runtime guard:] N/A
[Optional Fixes #Issue] N/A
[Optional Fixes commit #PR or SHA] N/A
[Optional Deprecated:] N/A
[Optional [API
Considerations](https://github.com/envoyproxy/envoy/blob/main/api/review_checklist.md):]
N/A

---------

Signed-off-by: Eitan Yarmush <eitan.yarmush@solo.io>
Signed-off-by: code <wbphub@gmail.com>
Co-authored-by: code <wbphub@gmail.com>

Mirrored from https://github.com/envoyproxy/envoy @ 9a474a30a1b9ecbfe1e9d1a5190ee8aef2b29041

envoy/service/ratelimit/v3/rls.proto

@@ -49,6 +49,8 @@ message RateLimitRequest {
 
   // Rate limit requests can optionally specify the number of hits a request adds to the matched
   // limit. If the value is not set in the message, a request increases the matched limit by 1.
+  // This value can be overridden by setting filter state value ``envoy.ratelimit.hits_addend``
+  // to the desired number. Invalid number (< 0) or number will be ignored.
   uint32 hits_addend = 3;
 }