config: Reuse the auto modules

[pellared]

trafficstars

Should we not take advantage of https://pkg.go.dev/go.opentelemetry.io/contrib/propagators/autoprop? Similarly for exporters we could use https://pkg.go.dev/go.opentelemetry.io/contrib/exporters/autoexport.

I think that the config is supposed to be extensible and allow custom exporters, processors, propagators. See: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/sdk.md#sdk-extension-components

Originally posted by @pellared in https://github.com/open-telemetry/opentelemetry-go-contrib/pull/6727#discussion_r1944603362