DataFrame.describe + auto-convert String-Err to RPolarsErr

[sorhawell]

Aim

use describe as occasion to rework RPolarsErr conversion behavior.

Before string errors and RPolarsErr where treated "equal". Now string errors will be upgraded to RPolarsErr. String errors can arise from legacy code with naive errors and from any base R function emitting errors.

Prior if an error was String it would propagate as that to the final error to the user.
Now R side result() and rust side unpack_r_result_list immediately upgrade errors to RPolarsErr.

RPolarsErr builds context in a more rigorous way and produces better traces of the error.

Summary of changes:

• >DataFrame>$describe()
• internal S3 method upgrade_err which can convert R errors and any legacy error into RPolarsErr.
• now when result() captures errors they will be upgraded with upgrade_err()
• .. also when R result_list unpacked any error will be upgraded to robj_to!
• replace protoProxyArray with robj_to! in select
• rework inner rust robj_to_rexpr being called by robj_to!
• no long support $select(list_1, list_2) on multiple lists args. Either input is one single arg which is one Expression a list of expressions. OR input is multiple args which are expressions. (this matches py-polars behavior)

[eitsupi]

Please auto formatting (make fmt GIT_DIF_TARGET=main)

[sorhawell]

make fmt GIT_DIF_TARGET=main

thx I misunderstood how to use make fmt

[eitsupi]

thx I misunderstood how to use make fmt

Yes, currently by default only uncommitted files are formatted, so you need to set GIT_DIF_TARGET=main to format after a commit.......

[sorhawell]

hmm maybe bad merge, seems like I'm reverting reverse -> descending PR

[eitsupi]

hmm maybe bad merge, seems like I'm reverting reverse -> descending PR

I think this is due to #291 (comment)

I will open a follow up PR...

[eitsupi]

Thanks!

[ddotta]

Awesome !