Wrapper for the tezos_smart_rollup_core host function definitions
as a safe API.
The rollup make host functions available to the kernel, as a set of C-style APIs. The
tezos_smart_rollup_core crate defines these as extern "C" functions
that are unsafe to call.
Using tezos_smart_rollup_host allows a kernel to access these capabilites
without relying on unsafe code.