_attempt_stream_socket re-implemented a narrow slice of the existing
_socket_from_stream helper (get_extra_info only) behind a blanket
try/except. Delegating to the shared helper keeps one socket-discovery
path (it already suppresses get_extra_info failures and covers the
_sock / anyio backends), and the remaining lookup cannot raise.
Also trims the close_attempt_stream docstring to the essential why.