python: Add support for exporting static class methods from c++

python: Add support for exporting static class methods from c++

This change adds support for exporting static methods in a c++
SimObject from the coressponsing python wrapper class. This will allow
us to define and use c++ methods without the need to instantiate an
object of the corresponding class.

Change-Id: Iaf24c1aa6f20feb5c91241f46ec8db005a6a0c0c
Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19168
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>