Hide / deprecate `rv ruby run` now that we have `rv run`

Now that we have rv run we don't need rv ruby run. Let deprecate it over the next few versions:

• [ ] Remove rv ruby run from the rv ruby help by annotating the subcommand with hide = true.
• [ ] Print a deprecation warning when rv ruby run is used, suggesting that the user run rv run --ruby VERSION COMMAND instead of rv ruby run VERSION COMMAND.
• [ ] Record which version the deprecation lands in, so we can remove rv ruby run 1 or 2 versions after we release the deprecation.