* feat: new method or aggregating multiple config changed subscriptions into one disposable object or more slim unsubscribing code
* refactor: moved nested private class declaration to bottom of class
* refactor: reusing stateful object in tests is not smart
* fix: invalid code for forming new array during InvokeList.Remove call
* refactor: extracted new sub-multiple builder into configuration manager extensions
* refactor: remove unused code
* refactor: removed UnSubscribeActionsDelegates
* refactor: whitespaces and renaming
---------
Co-authored-by: pa.pecherskij <pa.pecherskij@interfax.ru>