Proper division between "service" & "otelcol" packages

[djaglowski]

In #6723, I attempted to move component.Factories and componenttest.NopFactories to otelcol and otelcoltest, respectively. However, I was not able to identify a clear separation point between service and otelcol packages.

Additional context: #6723 (comment)

The immediate problems are:

1. Both otelcol and service contain many references to Factories.
2. otelcol contains many references to service.

Therefore, Factories can exist in service without causing import cycles, but the opposite is not true.

In order to move Factories to otelcol, we must determine which of the two points above should change. Should otelcol not depend on service, or should service not depend on Factories?

[bogdandrutu]

or should service not depend on Factories?

Done in #6774