Add: Flag to override oct and hex invalid separator removal

[Gabriele-Gentile]

Description

Boolean was added to simulate default behavior in Linux.
In hex, the separator is preserved for invalid values.
In oct, the separator is removed for invalid values.
We would like to add a flag to allow users the option controlling the default behavior.

Reason

To give user option to maintain consistency across the hex and oct functionality or keep it Linux-like.