Align configuration sources

OpenTelemetry must\* be configured from environment variables (conjecture: so that it is configured prior to the rest of the app and can instrument startup?).
blueapi is otherwise configured from yaml files but will soon support environment variables #495
If we deploy with tracing for local development/outside of Helm, this currently prevents us having a single source of truth to easily configure the instance.

\* Currently we think there is no other way to configure it

_Originally posted by @callumforrester in https://github.com/DiamondLightSource/blueapi/pull/719#pullrequestreview-2442055535_