Add ink! linting MVP stage (#431)

* Add ink! linting MVP stage

* CI: cache cargo installations; update versions

* Apply suggestions from code review

Co-authored-by: Sergejs Kostjucenko <[email protected]>

* Update changelog

* Check if `dylint` requirements are installed

* Make `clippy` happy

* Make tests happy

* Make `LICENSE` symlink

* Make error handling and panic's consistent

* Improve code structure

* Remove unneeded `--workspace`

* Fix `mapping-two-constructor` test file

* Simplify `Option<Vec<_>>` to `Vec`

* Generalize unsetting of env variables in `invoke_cargo`

* Move special case of `dylint` verbosity to call site

* Keep calm and return an `Err`

* Move checking for `dylint-link` to `build.rs`

* Add `ink_linting/Cargo.lock`

* Move `bool_to_exit_code` inline

* Add test for non-fully-qualified path call of `initialize_contract`

* Fix panic when no manifest path was supplied

* Improve structure of `build.rs...