Improve datetime handling in ScalarInequality and ScalarRange constraints

[amontanez24]

Problem Description

As a user, it would be useful if I could provide my datetime value as a string for the ScalarInequality and ScalarRange constraints. The synthetic data in the end should also match the same format as the input data.

Expected behavior

• Enforce that string values are used to define datetimes for the value parameter of the ScalarInequality constraint and the low_value and high_value parameters of the ScalarRange constraints.
• Enforce that the data after reverse_transform is in the same datetime format as the data that was fitted.
• Investigate the log warning that sometimes occurs when there are null values in the datetime column.

Additional context

• For the warning, investigate the cause. If it is a simple fix, implement in this issue, otherwise file another issue.