chore: filter empty multiaddrs in identify protocol

[dozyio]

Description

Add a check for empty multiaddrs from identify to stop them being added to the peer store.

Fixes #3478

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation if necessary (this includes comments as well)
• I have added tests that prove my fix is effective or that my feature works

[tabcat]

Issues:

• result.listenAddrs at utils.ts:172 still used raw message.listenAddrs.map(buf => multiaddr(buf)), so peer:identify consumers and the return value of identify.identify() still surfaced bare / to anything that read them.
• Malformed bytes would throw InvalidMultiaddrError at that same line after peerStore.patch had already run — partial-state failure, same crash class as fix(autonat-v2): spurious exceptions #3400.

Changes:

• Hoisted the cleaned listenAddrs once and reused it for both peer.addresses and result.listenAddrs.
• Folded the empty check into getCleanMultiaddr so it returns undefined for zero-byte multiaddrs too (also helps observedAddr in identify.ts:111).
• Added a junk-byte (Uint8Array.from([0xff, 0xff, 0xff])) test case — the existing new Uint8Array(0) short-circuits in getCleanMultiaddr before reaching the try/catch.