Use PSRule security audit tool and only test new bicep

[tonybaloney]

This changes the security testing to only test infra/main.bicep because at the moment it's picking up the ARM-compiled files in the project root and the ones in infra/PrevVersion.

It will close half of the active security issues on this project (which are duplicates)

[github-advanced-security]

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[markjbrown]

Thanks @tonybaloney will merge this. @sajeetharan please pull this latest into your branch before submitting PR on your changes.