Secure template changes for 16.0

What does this MR do and why?

Describe in detail what your merge request does and why.

Secure template changes for 16.0

This will include the majority of the changes to the stable Secure templates for 16.0

Please note that this does not contain any of the changes related to MR pipeline support.

Related Issue: Transition latest security templates to stable ... (#388988 - closed) • rossfuhrman • 16.0

MR acceptance checklist

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