[contracts] API host functions: remove `seal_` name prefix + enable aliasing (#12126)

* works but ugly

* refactored + renamed host fns

* fixed tests

* fix benchmarks

* updated marco docs

* Update frame/contracts/proc-macro/src/lib.rs

Co-authored-by: Alexander Theißen <alex.theissen@me.com>

* fix for the duplicated prefixed alias bug + test

* refactored a bit

* fix warnings + try to make macro rustdoc compile

* fmt after clearing

* examples update + nocompile

* add seal_ prefixes to unstable host functions

* updated after a review

Co-authored-by: Alexander Theißen <alex.theissen@me.com>