Update ToIntegerArrayVisitor tests with scalar conversion methods

It does not mean -0.1 rounds to -1.
The strategy of rounding to the nearest number, and when a number is halfway between two others, it's rounded toward the nearest number that's away from zero.
0.45 -> 0.5
0.5 -> 1.0
-0.45 -> -0.5
-0.5 -> -1

_Originally posted by @mobigliani in https://github.com/pyansys/ansys-common-variableinterop/pull/29#discussion_r848440651_

Locate the tests for ToIntegerArrayVisitor and read the existing scalar conversion cases first. Add coverage for the documented rounding examples, including positive and negative halfway values, then run the relevant test suite to confirm the expected conversions.

Written by the indexing model from the issue text.