control-connection: keep zero-token hosts

[dkropachev]

Summary

• keep zero-token nodes as topology members during control connection metadata refresh
• omit zero-token hosts from the token map
• expand unit coverage for system.peers, system.peers_v2, local row metadata, and empty token list shapes

Fixes #843

Driver surface

Control connection topology refresh and token metadata population.

Protocol or compatibility risks

Low. Token map behavior stays unchanged for hosts without tokens; the topology refresh no longer filters valid zero-token hosts from metadata.

Tests

• repo-ci fast: 044b625db0332d88a9741c3a707708b73f5d1b53dd140745f211e542e3cb0996

Integration scenarios

Not required; this is unit-covered metadata refresh behavior.

[dkropachev]

Withdrawing. This PR assumed zero-token nodes should remain in driver topology metadata while being omitted from the token map. That is likely the wrong model here: driver known hosts are query/pool targets, and zero-token nodes should not be added if the driver cannot execute on them.