Provide configuration examples in the YAML parser reference
Context
The YAML parser reference is generated from the docstrings of the various classes in buildgrid/_app/settings/parser.py
. This is the only place in the documentation where the full set of configuration options available is properly enumerated, but doesn't have any examples that make it immediately clear how to use them without additional context (see https://buildgrid.build/developer/reference_api.html#buildgrid._app.settings.parser.Remote for example).
We should add short example YAML snippets to the docstrings to clearly show how the tags are used, something like
- !remote-storage
url: http://remote-cas.example.org:50051/
instance_name: main
Acceptance Criteria
The YAML parser reference has some examples that are easy to understand at a glance, rather than only documenting as if its a Python API.