[FAST] Add basic NGFW enterprise stage

[LucaPrete]

A few notes:

• This is a separate L3 stage, so we don't duplicate code in networking stages
• This is using network firewall policies in addition to legacy firewall rules deployed in stage 2. In the future, if and when we'll migrate to firewall policies, we'll be able create the policies in stage 2 and add the new rules we need to the same policy in this stage.
• This PR doesn't take into account TLS inspection yet. It's complex and it would add many more pieces. To be added after this is merged, as a second step.

Checklist

I applicable, I acknowledge that I have:

• Read the contributing guide
• Ran terraform fmt on all modified files
• Regenerated the relevant README.md files using tools/tfdoc.py
• Made sure all relevant tests pass

[ludoo]

approving with a couple comments, we can discuss live if you want how/if to implement them (Julio also has comments)

[juliocc]

Looks good to me. The code is very clean and concise.

My only concern is the generous use of try as they tend to hide errors. Can you do a quick pass and remove those that are not necessary?