rename subnamespace Expr.arr to .list

[sorhawell]

pola-rs/polars#8999

[etiennebacher]

This has to be done at some point but it would bloat the code to keep both arr and list namespaces. I think we can replace all arr by list at once, which will be a massive breaking change. That could be worth a new release (maybe 0.8.1?).

What do you think @sorhawell @eitsupi ? I can deal with that if you agree

[sorhawell]

The subnamespaces can be moved around relatively easy. I can start a community PR with the namespace rerouting

Maybe the complete change could be done in two PRs

Patch update to 0.8.1 or so

• reroute arr subnamespace from Expr$arr to also Expr$list (~5 lines of r code)
• update docs to recommend list over arr + deprecation warning on arr (many search replace, but hopefully fast)

Minor update to 0.9 maybe

• close Expr$arr access
• rename internally to remove mentions of arr

[etiennebacher]

Sounds good to me. I think we could release 0.8.1 right after your "rerouting" PR and then take more time until 0.9.0 so that the deprecation notice is visible to the users at least for a few weeks

[etiennebacher]

arr is now deprecated and will be removed in 0.9.0