TLS and DoH: Avoid accessing non-atomic listener socket flags during HS/when accepting a connection
requested to merge artem-tls-doh-listeners-avoid-acessing-non-atomic-flags-on-handshake-or-accept into main
This merge request ensures that the non-atomic flags inside a TLS/DoH listener socket object (and associated worker) are accessed when doing handshake for a connection/accepting a connection only from within the context of the dedicated thread, but not other worker threads.
The purpose of this commit is to avoid TSAN errors during isc__nmsocket_closing() calls. It is a continuation of !7154 (merged)