Replace lazy_static with OnceLock inside monero-serai

lazy_static, if no_std environments were used, effectively required always
using spin locks. This resolves the ergonomics of that while adopting Rust std
code.

no_std does still use a spin based solution. Theoretically, we could use
atomics, yet writing our own Mutex wasn't a priority.

coins/monero/Cargo.toml

@@ -12,9 +12,10 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
+std-shims = { path = "../../common/std-shims", version = "0.1", default-features = false }
+
 futures = "0.3"
 
-lazy_static = "1"
 async-trait = "0.1"
 thiserror = "1"