NH-40928 - Removed containerid from k8s struct

[jerrytfleung]

Description of changes:

• It turns out that the containerid information is unnecessary for host-trace matching as it will be based on Pod information.
• Removed this field ASAP when we don't release to production yet.

Related issues

NH-40928

[cheempz]

Thanks @jerrytfleung. To be clear, the pod UID will be used for correlating APM Service to K8s at the pod level, but if our instrumentation is able to report container ID, there will be additional correlation between at the container level. So we do need the container ID field, just that we're asking instrumentation core libraries to set it in the existing HostID.dockerContainerID field, and for ingestion to use that field cc @gglogowski.