feat(net-cloudnat): add toggle for independent endpoint mapping and dynamic port allocation

[JSchwerberg]

No description provided.

[juliocc]

Thanks for this PR.

Can you update the README using tfdoc as explained in the contribution guide?

[JSchwerberg]

@juliocc Done :)

[JSchwerberg]

@juliocc slipping in some toggles for dynamic port allocation as well -- the current module is broken, with var.config_min_ports_per_vm being a no-op since dynamic port allocation isn't turned on by default. This fixes that, and adds a variable for config_max_ports_per_vm, as well as making sure that dynamic port allocation and independent endpoint mapping are mutually exclusive as required by the API.

extra changes require new review

[juliocc]

See inline comments, also make sure all tests and linting checks are passing.

[JSchwerberg]

See inline comments, also make sure all tests and linting checks are passing.

I'd love to, but that would mean Github would have to fix their 6 hour plus actions outage, so we'll have to re-run whenever they get their act together 😁

[JSchwerberg]

This is now passing linting and tests. Some test are failing on my machine locally, but are ENTIRELY unrelated to this PR and have to do with upstream changes in the firewall API, afaict.

cc @juliocc @ludoo