Doc: Feature deprecation and removal process documentation. #31980
Description
On #31278 we have seen that the process for deprecation and removing features is not well defined.
Would be good to have it written on the dev notes to follow always the same procedure in the future and avoid repeating the discussion.
We have different feature category, so a sub-section for each would be great.
- RPC (see wallet, rpc: deprecate settxfee and paytxfee #31278 as an example)
- Startup option
- Rest
- ZMQ
- Wallet settings
- In the future ( multiprocess interface)