[Issue-6991] Handle 429 errors from POST /internal/allowed via HookService

Related to issue: #6991

Change Summary

When Hooks are executed by Git processes, not directly by Gitaly. the error is being propagated via HookService.

When this happens, the message arrives back to Gitaly and treated as a generic failure. When a 429 error occurs, it gets written to stderr as a simple error message. The original rate-limiting context is lost, so it still returns INTERNAL status instead of RESOURCE_EXHAUSTED.

Proper error parsing is implemented in the pre_receive to detect rate-limiting errors from stderr and proper error propagation is done to return RESOURCE_EXHAUSTED instead of INTERNAL