refactor: centralize console worker connections

[EdsonPetry]

What changed

• Introduces one WorkerConnector abstraction for seed discovery and per-worker polling.
• Routes reconnects and discovered-worker URL parsing through the same connection policy.
• Preserves existing plaintext transport and bare-port CLI behavior.

Why

The console previously opened discovery and worker connections through separate paths. The follow-up PR needs both paths to apply identical logical-origin and physical-dial behavior for Fabric TLS.

Impact

No intended user-visible behavior change. This is the behavior-neutral base of the console stack.

Validation

• cargo fmt -p datafusion-distributed-console -- --check passed.
• Full local test/clippy builds exhausted host file descriptors while compiling aws-sdk-ec2, including with ulimit -n 8192.
• Official CI is required before merge.

Stack

1. This PR: centralize console connection creation.
2. #26: logical TLS worker origins and physical pod dialing.

Ports EdsonPetry/datafusion-distributed#2 to the DataDog compatibility branch.