The prior system spawned a new connection per request to enable parallelism,
yet kept hitting hyper::IncompleteMessages I couldn't track down. This
attempts to resolve those by a long-lived socket.
Halves the amount of requests per-authenticated RPC call, and accordingly is
likely still better overall.
I don't believe this is resolved yet but this is still worth pushing.
reqwest was replaced with hyper and hyper-rustls within monero-serai due to
reqwest *solely* offering a connection pool API. In the process, it was
demonstrated how quickly we can achieve equivalent functionality to reqwest for
our use cases with a fraction of the code.
This adds our own reqwest alternative to the tree, applying it to both
bitcoin-serai and message-queue. By doing so, bitcoin-serai decreases its tree
by 21 packages and the processor by 18. Cargo.lock decreases by 8 dependencies,
solely adding simple-request. Notably removed is openssl-sys and openssl.
One noted decrease functionality is the requirement on the system having
installed CA certificates. While we could fallback to the rustls certificates
if the system doesn't have any, that's blocked by
https://github.com/rustls/hyper-rustls/pulls/228.
