SSH is deployed inside Kubernetes cluster where rate limiting
at the application layer is unnecessary. Remove all SSH rate
limiter code:
- SshRateLimiter from SSHandle and SSHServer structs
- is_user_allowed checks in auth_publickey, auth_publickey_offered
- is_repo_access_allowed in exec_request
- is_ip_allowed in server::new_client
- rate_limiter module and start_cleanup
- Add retry_count to HookTask with serde(default) for backwards compat
- Limit hook task retries to MAX_RETRIES=5, discard after limit to prevent
infinite requeue loops that caused 'task nack'd and requeued' log spam
- Add nak_with_retry() in RedisConsumer to requeue with incremented count
- Standardize all slog logs: replace "info!(l, "msg"; "k" => v)" shorthand
with "info!(l, "{}", format!("msg k={}", v))" across ssh/authz.rs,
ssh/handle.rs, ssh/server.rs, hook/webhook_dispatch.rs, hook/pool/mod.rs
