Serve HTTP and REAPI gRPC on the same port

The cache server now handles both the HTTP cache API and REAPI gRPC traffic through a single listener, so you only need one cache port instead of separate HTTP and gRPC ports. For Tuist Bazel setups that rely on a single TUIST_CACHE_ENDPOINT, this fixes the REAPI GetCapabilities handshake that previously could land on the HTTP listener and cause a cold-cache fallback. Self-hosters can drop the old KURA_GRPC_PORT and KURA_GRPC_TLS_* settings and point gRPC clients at the same port as the HTTP cache (4000 by default, or 4443 for TLS). Public CLI/Bazel dial addresses remain unchanged.