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.

common/std-shims/Cargo.toml

@@ -13,7 +13,8 @@ all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
 
 [dependencies]
-hashbrown = "0.13"
+spin = "0.9"
+hashbrown = "0.14"
 
 [features]
 std = []