Document the minimal cloud requirements we need to work with another community's infrastructure

[choldgraf]

Context

In many cases we work with communities that wish to run their own cloud infrastructure projects / accounts / etc. For example, they might have their own billing account or a cloud project that already exists, and they wish to provide 2i2c access to it in order to manage the resources via our CI/CD repository.

However, in some cases this comes with extra restrictions, and we should document which kinds of restrictions are "too much" for us to be able to work with another group. This will help us communicate this to others and remember it for ourselves.

In a recent issue @yuvipanda listed what he thought were the most important pieces. We should confirm that this list is correct and, if so, document it publicly. Here's his quote:

@damianavila asked me to comment about what we would need from a cloud provider as 'requirements'. I think it's:

1. Making sure we (2i2c) have rights to grant unrestricted access to anyone we need in the cloud project
2. We have access to the billing tools so we can look at cost reports
3. There aren't additional technical restrictions in place enforced on us

Additionally, we support all the three major cloud providers, but at least personally I'd love for it to not be Azure haha :)

Originally posted by @yuvipanda in #1439 (comment)