usb-c: Generate USB-C connector VIF policies XML file

Generates XML file containing VIF policies by reading the device tree
using EDT.pickle generated during build
This script writes a subset of general and sink-pdo VIF policies in
output file
This script gets invoked during build if enabled through kconfig
The generated XML containing USB-C VIF policies could be used by
USB PD/Type-C analysers/testers to understand USB-C properties and
perform tests accordingly

Signed-off-by: Madhurima Paruchuri <mparuchuri@google.com>