Allow only scale=0 fixed-point values in fixed_width_column_wrapper

[davidwendt]

Description

The cudf::test::fixed_width_column_wrapper supports all fixed-width type including fixed-point types. However, there is no mechanism to specify the fixed-point scale value which is common for the entire column and stored in the column's type.
This fixes the case by throwing an error if a non-zero scale is specified for the input values in a fixed-point fixed_width_column_wrapper instance.

Also fixed several tests that incorrectly specified a non-zero scale.

Closes #16092

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[davidwendt]

/merge