Use WithFoo() arguments to autometrics.Init instead of long function signature

[gagbo]

Description

Instead of having a long function signature with various custom types for Init, we
use the With... option pattern to make the API easier to remember and use.

On top of that , as long as we provide default values, we can add extra initialization
arguments without making breaking changes.

Still todo (on top of the checklist below):

• Update the README with the new signature
• Update the examples so that they compile...
• ...and the main.go.orig too
• Remove the extra container structs that aren't used anymore (like PushConfiguration)

Fixes AM-141

Checklist

• The CHANGELOG is updated.
• The open-telemetry example in repository works fine:
  • the docker compose file is valid
  • the application compiles and run
  • alerts are getting triggered in Prometheus
• The prometheus example in repository works fine:
  • the docker compose file is valid
  • the application compiles and run
  • alerts are getting triggered in Prometheus
  • exemplars are accessible on the graph