[Deprecation] Explore deprecating the staking `chill` extrinsic

[emostov]

paritytech/substrate#8920 Introduces the chill_other extrinsic which allows anyone to chill a staker below Min{Nominator, Validator}Bond. The extrinsic also allows a controller to chill itself regardless of bonded funds, making the chill extrinsic redundant; thus we should consider deprecating the chill extrinsic.

### Deprecation steps
- [ ] Soft deprecation and removal from the codebase
- [ ] Update examples and tutorials
- [ ] Hard deprecation by adding a deprecate compiler warning
- [ ] Deprecation is noted in the release log
- [ ] Removal version is planned
- [ ] Deprecated feature is removed from the code base
- [ ] Removal of the feature is noted in the release log