CSV Vplans

Created by: silabs-robin

This PR adds a script to convert vplans from ".xlsx" to ".csv".

To be able to see a diff of vplan changes, it was proposed to save csv files next to the original spreadsheet files. The reason for the script is that Excel has severe localization quirks that makes it practically impossible to do reliably from their gui. For europeans defaulting to a ";" delimiter, a simple substitution of s/,/;/g is enough to make it workable. There is also included an example on the UserMode Vplan.

Note: If you click "View file" on the csv, Github actually renders it correctly.

Example diff: https://github.com/silabs-robin/core-v-verif/compare/vplan_csv...silabs-robin:core-v-verif:vplan_csv_demo