Remove tokio dependency from tendermint-machine

Indirects it via a minimal wrapper which can be trivially patched.

common/patchable-async-sleep/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "patchable-async-sleep"
+version = "0.1.0"
+description = "An async sleep function, patchable to the preferred runtime"
+license = "MIT"
+repository = "https://github.com/serai-dex/serai/tree/develop/common/patchable-async-sleep"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+keywords = ["async", "sleep", "tokio", "smol", "async-std"]
+edition = "2021"
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[lints]
+workspace = true
+
+[dependencies]
+tokio = { version = "1", default-features = false, features = [ "time"] }

common/patchable-async-sleep/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024 Luke Parker
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

common/patchable-async-sleep/README.md

@@ -0,0 +1,7 @@
+# Patchable Async Sleep
+
+An async sleep function, patchable to the preferred runtime.
+
+This crate is `tokio`-backed. Applications which don't want to use `tokio`
+should patch this crate to one which works witht heir preferred runtime. The
+point of it is to have a minimal API surface to trivially facilitate such work.

common/patchable-async-sleep/src/lib.rs

@@ -0,0 +1,10 @@
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+#![doc = include_str!("../README.md")]
+#![deny(missing_docs)]
+
+use core::time::Duration;
+
+/// Sleep for the specified duration.
+pub fn sleep(duration: Duration) -> impl core::future::Future<Output = ()> {
+  tokio::time::sleep(duration)
+}