Deprecate top-level service selection

[marctc]

We currently have two ways of service selection: top-level configuration (with fields like executable_name or open_port)
and using discovery > services section.

This causes some confusion as it not clear the rules of how filters are applied (see #1683) neither is documented.

We should indicate in the code a deprecation policy, and potentially remove it from the config in futures versions.

Remove it from docs. Places like service discovery docs or global properties are documenting these fields.

[marctc]

related #1206