Rename jsonpath method arg tokens

Rename jsonpath method arg tokens

This is just cleanup in the jsonpath grammar.

Rename the `csv_` tokens to `int_`, because they represent signed or
unsigned integers, as follows:

*   `csv_elem` => `int_elem`
*   `csv_list` => `int_list`
*   `opt_csv_list` => `opt_int_list`

Rename the `datetime_precision` tokens to `uint_arg`, as they represent
unsigned integers and will be useful for other methods in the future, as
follows:

*   `datetime_precision` => `uint_elem`
*   `opt_datetime_precision` => `opt_uint_arg`

Rename the `datetime_template` tokens to `str_arg`, as they represent
strings and will be useful for other methods in the future, as follows:

*   `datetime_template` => `str_elem`
*   `opt_datetime_template` => `opt_str_arg`

Author: David E. Wheeler <david@justatheory.com>
Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CA+v5N40sJF39m0v7h=QN86zGp0CUf9F1WKasnZy9nNVj_VhCZQ@mail.gmail.com