BUG: Fix display of CPU properties in application info. Fixes 0004176

Instead of explicitly computing the frequency and displaying the number
of cores, this commit updates the function "qSlicerApplication::displayApplicationInformations"
to:

• display the model name: The model name provides CPU vendor specific model and clock
  frequency in GHz.

• the number of logical processors.

Since the processor has a variable frequency (e.g. from 2.90GHz to 3.8 GHz
for the Intel E3-1535M), calling "GetProcessorClockFrequency()"
was returning a different result for each call.

Before:
CPU ......................: GenuineIntel 3.579 MHz, 1 cores

After:
CPU ......................: GenuineIntel Intel(R) Xeon(R) CPU E3-1535M v5 @ 2.90GHz, 1 cores, 8 logical processors

Co-authored-by: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>

From: Sankhesh Jhaveri <sankhesh.jhaveri@kitware.com>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@25142 3bd1e089-480b-0410-8dfb-8563597acbee