Render MAC addresses with bytes.hex(":")

[EONRaider]

Target: 1.4.0 (Tier 1 — earn the benchmark)

bytes_to_mac() (_base.py:48) is:

return ":".join(format(octet, "02x") for octet in data)

That runs seven generator steps, six format() calls and a join per
address — twice per Ethernet frame, plus once per NDP link-layer option
and per ARP hardware address. In a corpus profile the generator
expression alone accounts for 88,200 calls.

bytes.hex() has taken a separator argument since Python 3.8 and does
the whole thing in one C call.

Measured

300,000 calls: 0.350 s → 0.021 s — 16.5× faster.

What to do

return bytes(data).hex(":")

The bytes() wrapper keeps memoryview input working. Output is
identical: lowercase, colon-separated.

Acceptance criteria

• Output is byte-for-byte identical for all existing tests.
• memoryview input still works.