[C++] Enable multiple character delimiters in read_csv

[asfimport]

Read_CSV ParseOptions allows only a single character delimiter. Single character delimiters are highly susceptible to the candidate value existing within the data to be loaded, negating the ability to serve as a delimiter.

If a double character delimiter is used, the current limit of a single character returns "only single character unicode strings can be converted to Py_UCS4, got length 2"

Reporter: Jack Howard

_{Note: This issue was originally created as ARROW-17130. Please see the migration documentation for further details.}

[ajaytho]

Looking for multiple character delimiters in read and write. Many a times hex is used as delimiters which is multi-character and limitation for current implementation.