pingpong and btchat BT examples don't work well on all platforms

"Pingpong" and "btchat" are example applications that use classic bluetooth & service discovery protocol (SDP), and QBluetoothSocket to stream data (with Rfcomm ie. reliable transport protocol).

It seems the applications don't work well at the moment (tested with Qt ~6.3). Notably the client-servers are not able to find each other, or able to establish a socket connection, or something else.

This is to a testing task that attempts to find the main different root causes for these and will generate bugs for fixing if necessary.

Bugs:
QTBUG-99617 Windows (server) SDP write error
QTBUG-100042 Windows (server) pingpong service is not found
QTBUG-99685 Windows (client) device discovery never stops or misses devices
QTBUG-99687 Windows (client) scans just one discovered device for services
QTBUG-99689 Linux (Server) Windows (client) service scan filter fails
QTBUG-99673 macOS (client) SDP query doesn't invoke callbacks
QTBUG-99701 macOS (server) rfcomm bluetooth socket connection fails
QTBUG-100289 Windows, Linux btchat fails with a protocol error
QTBUG-100445 macOS (server) SDP anomalies
QTBUG-100303 macOS (client) unable to find services on Monterey

Unrelated to the pingpong and btchat examples, it seems that also the BT LE is broken on macOS 12
QTBUG-99703 (BT LE tests don't pass with macOS).