fix: drop xargs from postStart script

[Tehsmash]

xargs has inconsistant behaviour handling whitespace:

• When given argument -I {} it no longer splits on spaces properly.
• When given -d" " to force it to split on spaces it doesn't handle single values properly.

This problem identifies itself when there are multiple create models defined in the values today because xargs tries to put every model name in a single create command.

This commit drops the use of xargs completely from the script and uses the helm templating to create all the commands explictly.

Summary of changes:

Checklist:

• I updated the artifacthub.io/changes annotation in Chart.yml according to the documentation
• Optional: I updated in README.md the Helm Values

[jdetroyes]

Hello @Tehsmash

Thanks you for refactoring and optimizing postscript, indeed this is a better way to handle model lists commands.