chore/error: remove from str conversion and add deprecation notificat… (#7472)

* chore/error: remove from str conversion and add deprecation notifications

* fixup changes

* fix test looking for gone ::Msg variant

* another test fix

* one is duplicate, the other is not, so duplicates reported are n-1

* darn spaces

Co-authored-by: Andronik Ordian <write@reusable.software>

* remove pointless doc comments of error variants without any value

* low hanging fruits (for a tall person)

* moar error type variants

* avoid the storage modules for now

They are in need of a refactor, and the pain is rather large
removing all String error and DefaultError occurences.

* chore remove pointless error generic

* fix test for mocks, add a bunch of non_exhaustive

* max line width

* test fixes due to error changes

* fin

* error outputs... again

* undo stderr adjustments

* Update client/consensus/slots/src/lib.rs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* remove closure clutter

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* more error types

* introduce ApiError

* extract Mock error

* ApiError refactor

* even more error types

* the last for now

* chore unused deps

* another extraction

* reduce should panic, due to extended error messages

* error test happiness

* shift error lines by one

* doc tests

* white space

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Into -> From

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* remove pointless codec

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* avoid pointless self import

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

Co-authored-by: Bernhard Schuster <bernhard@parity.io>
Co-authored-by: Andronik Ordian <write@reusable.software>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>