doxygen group common_utils containing low level utilities for layout engines

Directory common/lib contains more than 50 source file. Such a lengthy list of files is challenging to observe and comprehend.

To enhance navigation within the source code, it beneficial to organize these files into subgroups.

Organize almost independent from the rest of the directory and loosely coupled files into the common_utils group.

By structuring the files into such subgroups, developers can more easily locate relevant code and understand its purpose within the project architecture.

Objects usage diagram for directory common: Generated from output of nm.