[extension/observer/docker] add ListAndWatch to observer

[mstumpfx]

Description: Adds the ListAndWatch capability to the Docker observer, and integration tests to help support it. There will be another PR after this one to add watching the docker container events stream to ListAndWatch to help modify endpoints in more real time, out of of the initial load and cache refresh interval.

Link to tracking Issue: #4446

Testing: Added new integration tests to test for some observer functionality. More will be added in the next PR when the container event stream is being watched and used to add/update/remove endpoints.

[rmfitzpatrick]

Not introduced here, but I remembered that the receiver creator uses endpoint target scheme of host/ip:port so the existing target functionality would require setting ports manually in target receiver configs**: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/extension/observer/k8sobserver/handler.go#L88

[mstumpfx]

Not introduced here, but I remembered that the receiver creator uses endpoint target scheme of host/ip:port so the existing target functionality would require setting ports manually in target receiver configs**: https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/extension/observer/k8sobserver/handler.go#L88

@rmfitzpatrick good catch, thanks, I just updated the target in this PR.

[dmitryax]

Please rebase