Without this change, aio used with HTTP/2 can result in connection hang,
as observed with "aio threads; aio_write on;" and proxying (ticket #2248).

The problem is that HTTP/2 updates buffers outside of the output filters
(notably, marks them as sent), and then posts a write event to call
output filters.  If a filter does not call the next one for some reason
(for example, because of an AIO operation in progress), this might
result in a state when the owner of a buffer already called
ngx_chain_update_chains() and can reuse the buffer, while the same buffer
is still sitting in the busy chain of some other filter.

In the particular case a buffer was sitting in output chain's ctx->busy,
and was reused by event pipe.  Output chain's ctx->busy was permanently
blocked by it, and this resulted in connection hang.

Fix is to change ngx_chain_update_chains() to skip buffers from other
modules unconditionally, without trying to wait for these buffers to
become empty.

With SSL it is possible that an established connection is ready for
reading after the handshake.  Further, events might be already disabled
in case of level-triggered event methods.  If this happens and
ngx_http_upstream_send_request() blocks waiting for some data from
the upstream, such as flow control in case of gRPC, the connection
will time out due to no read events on the upstream connection.

Fix is to explicitly check the c->read->ready flag if sending request
blocks and post a read event if it is set.

Note that while it is possible to modify ngx_ssl_handshake() to keep
read events active, this won't completely resolve the issue, since
there can be data already received during the SSL handshake
(see 573bd30e46b4).

A new behaviour was introduced in OpenSSL 1.1.1e, when a peer does not send
close_notify before closing the connection.  Previously, it was to return
SSL_ERROR_SYSCALL with errno 0, known since at least OpenSSL 0.9.7, and is
handled gracefully in nginx.  Now it returns SSL_ERROR_SSL with a distinct
reason SSL_R_UNEXPECTED_EOF_WHILE_READING ("unexpected eof while reading").
This leads to critical errors seen in nginx within various routines such as
SSL_do_handshake(), SSL_read(), SSL_shutdown().  The behaviour was restored
in OpenSSL 1.1.1f, but presents in OpenSSL 3.0 by default.

Use of the SSL_OP_IGNORE_UNEXPECTED_EOF option added in OpenSSL 3.0 allows
to set a compatible behaviour to return SSL_ERROR_ZERO_RETURN:
https://git.openssl.org/?p=openssl.git;a=commitdiff;h=09b90e0

See for additional details: https://github.com/openssl/openssl/issues/11381

The OPENSSL_SUPPRESS_DEPRECATED macro is used to suppress deprecation warnings.
This covers Session Tickets keys, SSL Engine, DH low level API for DHE ciphers.

Unlike OPENSSL_API_COMPAT, it works well with OpenSSL built with no-deprecated.
In particular, it doesn't unhide various macros in OpenSSL includes, which are
meant to be hidden under OPENSSL_NO_DEPRECATED.

ERR_peek_error_line_data() was deprecated in favour of ERR_peek_error_all().
Here we use the ERR_peek_error_data() helper to pass only used arguments.

Using PEM_read_bio_DHparams() and SSL_CTX_set_tmp_dh() is deprecated
as part of deprecating the low level DH functions in favor of EVP_PKEY:
https://git.openssl.org/?p=openssl.git;a=commitdiff;h=163f6dc

Switch to SSL_get1_peer_certificate() when building with OpenSSL 3.0
and OPENSSL_NO_DEPRECATED defined.