* Gav wrote this code in pull #10195. Extracting to simplify that PR.
* fix potential panics
* prevent panics in slide
* update doc
* fmt
* Update frame/support/src/storage/bounded_vec.rs
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>
Co-authored-by: Gav Wood <gavin@parity.io>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>