Decimal values in SLT tests lose display precision if they have trailing zeros

[AdamGS]

As noted by @kosiew in #22714 (comment), decimals lose some of their precision in some cases.

This fact is surprising to me because one of the changes I tried to make in #23161 was to make decimal rendering in the tests more consistent and avoid implicit rounding of values.

For example, currently the following SLT statement fails:

query R
select arrow_cast('1.2300', 'Decimal32(9, 4)');
----
1.2300

The actual return value is 1.23

[theirix]

take