Reject port ranges in `discovery.seed_hosts`

[DaveCTurner]

Today Elasticsearch accepts, but silently ignores, port ranges in the discovery.seed_hosts setting:

discovery.seed_hosts: 10.1.2.3:9300-9400

Silently ignoring part of a setting is trappy and we should instead reject this setting if it contains port ranges like this.

[elasticmachine]

Pinging @elastic/es-distributed

[Hohol]

I'd like to work on this. Could you assign me please?

[DaveCTurner]

Hi @Hohol, I can't assign issues outside of the Elastic organisation, but you're welcome to work on this.

[Hohol]

@DaveCTurner I've made a PR #41404