floss: DisplayAddress: Follow LibBluetooth style

Follow RawAddress::ToRedactedStringForLogging
- Lowercase
- Don't redact if the address is ff:ff:ff:ff:ff:ff or 00:00:00:00:00:00

Bug: 342337056
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: build-in-container.py (Rust unittest)
Flag: EXEMPT, Floss-only changes
Change-Id: If333f1594aebcc29456c500ccad5d3df614be781