Enable sniffing of HCI packets to std::ostream

This allows for the registration of an ostream on the hci sniffer. This
can be used by external parties to sniff hci packets and write them to
different streams.

Bug: 231598376
Bug: 199325666
Bug: 241962982
Tag: #refactor
Test: Two emulators can discover each other
Test: gd/cert/run
Ignore-AOSP-First: Cherry-picked from AOSP
Merged-In: I0622263eaec8dd360d893817dd6a73f30a15af5f
Change-Id: I0622263eaec8dd360d893817dd6a73f30a15af5f