Add a mp-config Galleon layer

As we work on adding MP OpenAPI, MP JWT and MP FT, we're going to want to add a Galleon layer for each in order to allow customization of the precise set of functionality a user wants.

Each of these has a dependency on MP Config, so we should add a layer independent of the current 'observability' layer so the other layers can depend on config without provisioning health/metrics/opentracing.

The 'observability' layer itself would depend on mp-config.