feat: migrate and move all metadata to be only owned and managed in a DB collection on `telemetry_int`

[viniarck]

This is for a future discussion to consider letting telemetry_int to manage and own all metadata related values in a new DB collection.

Current potential pain points:

• If an interface proxy_port changes, it'll be updated and handled, but the user needs to list again the EVCs to understand if an invalid value was set due to this being managed by topology and telemetry_int only reacting to the events. This has been elaborated and explained on feat: validation to only support one UNI per proxy port #110 check out for more information
• EVC telemetry metadata getting accidentally deleted, this is rate but can happen if someone changes or delete it directly on topology, enable or disable INT will still work if you force it though. But it's a similar argument where metadata mistakes can leave things in a problematic state.

Historically, as justified in the blueprint it was intentional to use metadata to facilitate, but there are these potential points that Ops are finding inconvenient to deal with.