This function was incorrectly processing refdeses like "U1000".
Change the algorithm to a simpler STL-compatible one and
update the tests.
Fixes: lp:1813669
* https://bugs.launchpad.net/kicad/+bug/1813669
This breaks the following functions out to a general-purposed refdes utils
header:
* MODULE::GetReferencePrefix()
* kicad_string.h RefDesStringCompare()
This acheives:
* Slimming of MODULE interface
* Placement of refdes code in common rather than pcbnew
** Testing of this code in qa_common
* Tighter and smaller includes for code that only needed refdes functions
Note: there are failing tests commited (as expected failures). These
are the cause of lp:1813669 and will be fixed as a follow-up commit.
John Beard