cuprated: Add graceful shutdown #3363

Job	Run time
ci-docker (fedora:latest, dnf install --assumeyes @development-tools gcc gcc-c++ cmake git openss...	1h 13m 52s
wasm-32-bit-support (cuprate-epee-encoding)	2m 39s
ci (macos-15)	1h 20m 26s
ci-docker (debian:stable, apt update && apt -y install build-essential curl cmake git pkg-config ...	1h 14m 54s
fmt	23s
ci (windows-2022)	2h 15m 35s
ci (ubuntu-24.04)	1h 12m 44s
typo	18s
wasm-32-bit-support (cuprate-rpc-types)	5m 25s
wasm-32-bit-support (cuprate-fixed-bytes)	1m 50s
ci (ubuntu-24.04-arm)	53m 25s
ci-docker (archlinux:latest, pacman -Syyu --noconfirm base-devel git cmake openssl)	1h 17m 1s
	9h 38m 32s

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