[ArrowStringArray] REF: extract/extractall column names
thanks @simonjayhawkins 

wouldn't object to moar tests the column naming already seems to be extensively tested in the extract/extractall tests with named groups, unnamed groups, some unnamed groups, one group, two groups etc.

this is a precursor to #41372, same for extractall and then the dispatch to pyarrow kernels and perf opt of the object fallback. will add tests where there appear to be gaps. (but I don't think DataFrame column names or Index/Series names is one of those gaps)