Support DelayedCloseTimeout

*Description*:
>Describe the desired behavior, what scenario it enables and how it
would be used.

The delayed close timeout is for downstream connections managed by the HTTP connection manager.
It is defined as a grace period after connection close processing has been locally initiated
during which Envoy will wait for the peer to close (i.e., a TCP FIN/RST is received by Envoy
from the downstream connection) prior to Envoy closing the socket associated with that
connection.

[optional *Relevant Links*:]
>Any extra documentation required to understand the issue.