[Issue] AZD should support custom clouds

- [x] Make sure you've installed the latest version using [instructions](https://github.com/Azure/azure-dev?tab=readme-ov-file#installupgrade-azure-developer-cli)

**Output from `azd version`**
azd version 1.23.11 (commit 8a12ac217ec685745fa195698b3c84387c922b2b)

**Describe the bug**
`azd` is unable to talk to a custom cloud (or even the German cloud), as only three clouds are supported: 'AzureCloud', 'AzureChinaCloud', 'AzureUSGovernment'

**To Reproduce**
> az cloud register --name CustomCloud --endpoint-resource-manager https://management.azure.com
> az cloud set --name CustomCloud
> azd config set cloud.name CustomCloud
> azd up --debug

**Expected behavior**
I'd expect `azd` to look at the clouds configured using `az`.

**Additional context**
Screenshot of the current behaviour: