[beyla.ebpf] Allow using a standard Beyla config file

[Amoolaa]

Request

It would be nice if we could use a standard Beyla config file and point to it from Alloy rather than use the Alloy-fied syntax.

This is also what blackbox exporter does.

Use case

Helps to move people off using the standalone Beyla and onto the embedded Beyla within Alloy, while still utilising the native config