add(arch): catalog for 3-tier web app architecture

[eddie-knight]

This PR attempts to demonstrate what it could look like to draw elements from service-specific control catalogs into a control catalog for a reference architecture.

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[eddie-knight]

@mlysaght2017 What do you think of this approach?

[mlysaght2017]

Looks good!

[github-actions]

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[eddie-knight]

I think this is in a reasonable state, ready for addition of the actual threats and controls.

If the team prefers, I can make the relevant ci changes first in a separate PR:

• PR Title checker won't currently pass because this adds arch as a new option
• yaml-checker won't pass because this modifies the expectations for metadata — all metadata files will need updated to comply with this schema

[damienjburks]

This is so dope! Love it 🔥