Up till now all send errors have been translated into a generic
{error, closed}. This patch allows {error, econnreset} to be
returned on send errors when it is detected that the TCP peer
has sent an RST.

An ECONNRESET is a socket error which tells us that a TCP peer has sent
an RST. The RST indicates that they have aborted the connection and
that the payload we have received should not be considered complete. Up
until now, the implementation of TCP in inet_drv.c has hidden the
receipt of the RST from the user, treating it as though it was just
a FIN terminating the read side of the socket.

There are many cases where user code needs to be able to distinguish
between a socket that was closed normally and one that was aborted.
Setting the option {show_econnreset, true} enables the user to receive
ECONNRESET errors on both active and passive sockets.

A connected socket returned from gen_tcp:accept/1 will inherit the
show_econnreset setting of the listening socket.

By default this option is set to {show_econnreset, false}.

Note that this patch only enables the reporting of ECONNRESET when
the socket is being read from. It does not report ECONNRESET (or
EPIPE) when the user tries to write to a connection when an RST
has already been received. Currently the TCP implementation in
inet_drv.c hides all such send errors from the user in favour
of returning {error, close}. A separate patch will be needed to
enable the reporting of such errors.

OTP-12797

* richcarl/warnings-by-default/OTP-12781:
  stdlib: Use warning channel in test qlc_SUITE:otp_6964/1
  stdlib: Fix testcase for qlc_SUITE
  kernel: Fix code_SUITE with respect to new logger default
  Map error logger warnings to warning messages by default

Also fix and document the broken +We option.

This reverts commit 4c4d7fa40e5fb59854724ce74b8aa3546525cb90.

This pr is causing some test failures that were missed at first.