Deprecate Channel.select splat overloads

[straight-shoota]

The splat-receiving overloads of Channel.select and Channel.blocking_select are internal methods (:nodoc:) but never used internally. They can be removed. This patch only adds a deprecation, but it would probably be fine to just drop them entirely.

They used to be part of the public select API. After the introduction of the select keyword in #3130 they remained visible, but became nodoc in #9564.

[bcardiff]

I thought the compiler will emit call to the splat overloads. But the expanded calls use Channel.non_blocking_select({ch.send_select_action}) instead of Channel.non_blocking_select(ch.send_select_action) as I thought.

I would prefer to this splat overloads to remain. So the compiler could emit the later and we can add overloads for optimized version for single/double channel actions.

Of course we can check on the indexable size on runtime, so it's not big deal if we deprecate them.

[sdogruyol]

Thank you @straight-shoota 🙏

[straight-shoota]

Draft for now because it's not clear whether we might want to keep using these overloads.