[contracts] define_env! re-write as a proc macro (paritytech#11888)

* define_env proc macro basics + can_satisfy part ready

* expand_impls part done

* fix of the &FunctionType bug

* pallet is compiled

* updated host fn definition syntax

* docs comments allowed to host fn definitions

* all 53 host funcs re-defined by the new macro

* unstable feat fix

* cleanup

* legacy mbe macros cleaned up

* Added Env ident to macro attribute; all tests pass!

* \#[v(..)] -> \#[version(..)]

* some tiny corrections

* save

* builds with non-magic rt; tests fail

* tests pass

* refactored errors + added docs

* merge err fixed

* fixes on @ascjones review, all except moving away from `pub mod env` syntax

* debug printing cleared

* clippy fix