Operate as a config server

Similar to spring boot, Aspire should be able to operate as a centralised configuration server for all micro services.

To achieve this a few milestones will need to be delivered mainly:
- Definition of config sets schema which is obtained from the configuration layer. Needs to define for keys aspects such as min/max length, data type, validation rules etc
- Configuration Provider API (Rest &/or gRPC). Allows for fetching of config with atleast 2 param's (App, environment) required & an optional Filter. The filter limits the settings which are returned and is applied starting from the start of the key.
- implementation of a Microsoft.Extensions.Configuration.Aspire package which consumes the api and loads config into the micrpservices
- internal API implemented to provide the ability to set values of properties and needed for UI
- Dashboard is extended to facilitate setting of configuration values via UI
- API provided to push configuration sets into the server so they can be configured