environment() function is missing latest metadata

**Bicep version**
n/a

**Describe the bug**
The environment() function can be used to pull information about the current cloud, primary use case is endpoints that vary across clouds. As new endpoints are added, they are often not added to this function that is backed by this api: https://management.azure.com/metadata/endpoints?api-version=2019-05-01

**Additional context**
We need a process to keep this updated, in the meantime, we can use this issue to track things we identify are missing.

The issue identifies the management.azure.com metadata endpoint as the source for environment() data, but names no implementation file or test. Start by locating the environment() implementation and comparing its supported metadata with that endpoint; done would require a defined way to keep the function's metadata current, plus coverage for the missing information.

Written by the indexing model from the issue text.