coalesce function is unable to compare the value from a String field against a string literal

coalesce function is unable to compare the value from a String field against a string literal

PR https://github.com/apache/pinot/pull/9958 enables coalesce to support string literals but still coalesce is unable to compare a string field value against a string literal. For example:

select coalesce(my_string_field,'1234') from my_table limit 1

doesn't work, gives an error
Caused by: java.lang.IllegalArgumentException: Argument types have to be the same.

Start by reproducing the issue with `select coalesce(my_string_field,'1234') from my_table limit 1` and trace the coalesce argument type validation. Done means a String field can be compared with a string literal without the "Argument types have to be the same" error, while existing coalesce behavior remains intact.

Written by the indexing model from the issue text.