Explain more on running Crossplane at scale

### What's Missing?

I would like to have more documentation on running crossplane at scale. There is [multi-tenant][multi-tent] documentation
available. What i am missing

#### Maximum amount of managed resources in a etcd, based on number or size

For example GCP has a ( i think pretty hard) limit of 6GB for etcd. When is 6GB a limiting factor? Is the amount of objects a the only limiting factor here or are there other processes (maybe internal migration of objects) also important.

#### Cloud vendor specific docs

Any specific things we need to know on using a specific cloud vender. There are two tracks here I think. Running the controlplane
on a (managed) kubernetes would be one. An other one might be more related to provider-\ and i guess that should go into the provider docs.

[multi-tent]: https://docs.crossplane.io/knowledge-base/guides/multi-tenant/