refactor(share/shwap/p2p/shrex): Remove rate-limiting middleware

[renaynay]

Overrides #4333

Argument for removal:

1. We implemented middleware preemptively without a metric driving that decision and the default ConcurrencyLimit was chosen without a proper analysis backing the choice. BNs can handle far more requests than the conservative ConcurrencyLimit, especially given no shrex-eds pressure.
2. This middleware is much easier to "attack" than it is useful. Attacker may fill ConcurrencyLimit worth of slots with bogus requests, effectively occupying server's serving capacity with garbage while real requests are routed elsewhere, rendering server useless.
3. Libp2p provides implicit "rate-limiting" via conn + resource managers, dropping inbound requests when exceeding limits set by resource manager. Currently, we allow InfiniteLimits for BNs, but we can configure per-protocol resource limits if we see fit.