[demo] Splitting into modules

[puckpuck]

The OpenTelemetry Demo is moving to a modules-based deployment, with a core set of components and several optional modules, as well as a full or all mode where everything is included.

What should be the best way to approach this? To be considered in all of this, the Helm chart does not need to follow the Demo's non-Kubernetes (docker compose) deployment model. What works best for Helm/K8s should be considered and followed here while following the premise to break the Demo into multiple modules.

The Collector uses the presets construct, which may serve well here. Docker compose offers an override mechanism that differs from Helm. In Docker compose, environment variables, and volumes are additive, but these constructs are replaced in Helm.

This functionality will need to allow for the following:

• enable additional components
• upsert items to the env and volumes arrays associated with any component
• modify resource limits for any component
• modify the OpenTelemetry collector configuration (via presets and/or standard config options)