Signed-off-by: A. Jesse Jiryu Davis <jesse@mongodb.com>

Signed-off-by: A. Jesse Jiryu Davis <jesse@mongodb.com>

collection_watch runs an aggregate command with
collection_read_command_with_opts and then creates a cursor with
cursor_new_from_command_reply. To ensure they use the same implicit
session lsid, the change_stream_t must be responsible for creating
the implicit session and pass this session to both the command and
cursor as if it were an explicit session.

Signed-off-by: A. Jesse Jiryu Davis <jesse@mongodb.com>

Signed-off-by: A. Jesse Jiryu Davis <jesse@mongodb.com>

Signed-off-by: A. Jesse Jiryu Davis <jesse@mongodb.com>

Signed-off-by: A. Jesse Jiryu Davis <jesse@mongodb.com>

Starting in commit #9f9934dc, the driver had incorrectly called "ping"
before nearly every command when in single-threaded mode. This was due
to the mongoc_topology_scanner_node_t.last_update field not being
updated, so the driver thought each server's socket had been idle and
needed to be checked with "ping", even when the socket had been used
recently.

In this commit, update last_used after every command so we don't call
"ping" unnecessarily.