Cross-contract calling: simple debugger (#14678)

* Provide basic breakpoints

* Rename to Observer

* Rename feature. Single trait. Borrow-checker

* : frame_system::Config

* Confused type name

* Minor bugs

* pub trait

* No unnecessary cloning

* Make node compile with all features

* Move everything debug-related to a single module

* Add docs and implementation for ()

* fmt

* Make it feature-gated or for tests

* Prepare testing kit

* Testcase

* Fmt

* Use feature in dev-deps

* ?

* feature propagation

* AAAA

* lol, that doesn't make much sense to me

* Turn on

* clippy

* Remove self dep

* fmt, feature-gating test

* Noop to trigger CI

* idk

* add feature to pipeline

* Corrupt test to see if it is actually being run

* Revert change

* Doc for conf type

* Review

* Imports

* ...

* Remove debug for kitchen-sink

* Move test

* Fix imports

* I must have already tried this one...