Arm backend: add VGF runtime accuracy comparisons (pytorch#21396)

Change-Id: I3807992095a75caa687081ed7a25a0c2b664d524
Signed-off-by: Rob Elliott <Robert.Elliott@arm.com>

Add pte execution using runtime python bindings, and additional stats to
ensure export and quant accuracy is maintained through the whole
pipeline as further optimisations are explored.

cc @digantdesai @freddan80 @per @zingo @oscarandersson8218 @mansnils
@Sebastian-Larsson @rascani

Author: robell