sc-executor-wasmtime: leverage shared host functions

[pepyakin]

At the moment of writing, wasmtime is about to introduce a concept of shared host functions,

bytecodealliance/rfcs#9
bytecodealliance/wasmtime#2625

This would allow us to not redefine the entire Substrate Runtime Interface upon each WasmModule instantiation. While it's not important for the substrate path it may be useful for PVF execution, since there we may execute a lot of short lived instances with the same interface.

See also #8251 for a prerequisite refactoring and #8153

[stale]

Hey, is anyone still working on this? Due to the inactivity this issue has been automatically marked as stale. It will be closed if no further activity occurs. Thank you for your contributions.