Create post upgrade task function to check kptfile for upstream chart changes

Add a function to post upgrade tasks functions.sh to check for a chart/Kptfile if it exists search upstream for new version and add the command to allowedPostUpgradeCommands. This will then be added to every package renovate.json in this issue https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues/1110 to add a comment on the package MR for the developer to run kpt update.

an example script of how that can be done is in the description of this MR https://repo1.dso.mil/groups/platform-one/big-bang/-/epics/180