Remove xHAL remnants from gemhardware

Summary

During the migration to the mono-repository, xHAL has been split into different parts, some of them being directly included into gemhardware. The following files can be found inside the gemhardware source directory:

• src/XHALXMLNode.h
• src/XHALXMLParser.cpp
• src/XHALXMLParser.h

In addition to a much-needed renaming and refactoring, no functions or classes should be declared in the xhal namespace if not belonging to the xhal libraries (stored in the xhal folder).

Steps to reproduce

The gemhardware package contains parts of what used to be xHAL.

What is the expected correct behavior?

The gemhardware package should not contain parts of what used to be xHAL: xHAL is a hardware abstraction library; gemhardware contains the low-level code accessing the GEM hardware.