Updater verification (#8787)

* getting started

* refactor main

* unwrap_or -> unwrap_or_else

* force parity to lower version number to trigger update

* Fix typos

* formating

* some minor refactoring

* enable lints and fix some warnings

* make it compile

* minor tweaks to make it work

* address review comments

* Rename exe to exe_path and minor import changes

* updater: unreleased -> unknown

* Add `debug` configuration to force parity-updater

* Introduce a new feature `test-updater` in order conditionally hardcode
the version number in parity in order to force an update
* This should only be used for debug/dev purposes

* nits

* Pulled latest submodule of `wasm-tests`