Merged overloaded commands

[ayax79]

• fixes dfr min stoped working with dfr col in 0.83.0 #9807

Description

This pull request merges all overloaded dfr commands into one command:

eager:
dfr first -> eager/first.rs
dfr last -> eager/last.rs
dfr into-nu -> eager/to_nu.rs (merged)

lazy:
dfr min -> expressions/expressions_macro.rs lazy_expressions_macro
dfr max -> expressions/expressions_macro.rs lazy_expressions_macro
dfr sum -> expressions/expressions_macro.rs lazy_expressions_macro
dfr mean -> expressions/expressions_macro.rs lazy_expressions_macro
dfr std -> expressions/expressions_macro.rs lazy_expressions_macro
dfr var -> expressions/expressions_macro.rs lazy_expressions_macro

series:
dfr n-unique -> series/n_unique.rs
dfr is-not-null -> series/masks/is_not_null.rs
dfr is-null -> series/masks/is_null.rs

User-Facing Changes

No user facing changes

[amtoine]

hi @ayax79 👋 😋
thanks again for working on the dataframes 🙏

could you make the title of the PR a bit smaller so that it fits in one line? 😋
it looks like it's the first commit's title which is a bit too long 😮

i'll mark this as a DRAFT for now as you have a "WIP" in the description 😌

[fdncred]

Most of the conversations related to this PR are here https://discord.com/channels/601130461678272522/1134562453817151528

[WindSoilder]

Thanks for the pr! I like it very much.

[ayax79]

@amtoine, updated and the PR is ready to go.

[WindSoilder]

I love the updated description :-)

[fdncred]

Thanks for working on this. I think dfrs are still a bit of a mess but this at least gets us back to working order. Thanks so much for putting in the time and effort to get us to this point @ayax79!