Introduce protobuf versioning before 2.0 release to avoid supporting deprecated 1.x functionalities.

Summary of changes:

• split protos into v1 and v2 packages, so both legacy and latest versions can use the same repo
• introduce a more standardized naming convention for packages
• align enum variant naming with linter rules
• add a dedicated client_types package so both v1 and v2 proxy supports existing desktop/mobile clients
• clean up deprecated fields
• fix field numbering for messages with removed fields
• change latest_timestamp field in PeerStats message to actual Timestamp to not discard sub-second precision
• add CI tests

v1 modules are supposed to be a snapshot of the main branch so legacy services can also be migrated to this version.

Related DefGuard/defguard#2414

PRs updating specific services:

• support protobuf versioning defguard#2458
• support protobuf versioning proxy#262
• support protobuf versioning gateway#292