feat: add new metrics

[sbackend123]

Checklist

• I have read the coding guide.
• My change requires a documentation update, and I have done it.
• I have added tests to cover my changes.
• I have filled out the description and linked the related issues.

Description

• Add transport label to libp2p created/handled connection metrics (tcp / ws / wss / quic*).
• Move /wss + QUIC classification into bzz.ClassifyTransport.
• Replace separate public/private counters with public="true|false" on handled_connection_count.
• Pre-init label series so unused transports show as 0, not missing.

Breaking changes

• created_connection_count / handled_connection_count: Counter → CounterVec.
• handled_connection_count now has labels {transport, public}.
• Removed public_address_connections_total / private_address_connections_total — use handled_connection_count{public=...} instead.
• Dashboards using count(...) as a denominator will under-count after upgrade; prefer sum by (...).

Open API Spec Version Changes (if applicable)

Motivation and Context (Optional)

Related Issue (Optional)

#5506

Screenshots (if appropriate):

AI Disclosure

• This PR contains code that has been generated by an LLM.
• I have reviewed the AI generated code thoroughly.
• I possess the technical expertise to responsibly review the code generated in this PR.