Remove tokio dependency from tendermint-machine

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

.github/workflows/common-tests.yml

@@ -27,6 +27,7 @@ jobs:
           GITHUB_CI=true RUST_BACKTRACE=1 cargo test --all-features \
             -p std-shims \
             -p zalloc \
+            -p patchable-async-sleep \
             -p serai-db \
             -p serai-env \
             -p simple-request