Better handling of tls and early data buffer

This reverts commit 14dfeee4.

This fixes that nghttpx stalls when TLS handshake and data follow
after proxy protocol header and no extra read notification is
triggered (e.g., just small 1 HTTP request).

Don't send RST_STREAM to idle stream

doc: clarify flow control behaviour for nghttp2_session_send()

The previous wording implied that if send_callback doesn't return
NGHTTP2_ERR_WOULDBLOCK, this function would always send all
submitted requests / data. This is not the case, since flow control can
cause some data to remain queued until WINDOW_UPDATE is received.

Signed-off-by: Asra Ali <asraa@google.com>

Implement max settings option

This reverts commit b7d16101.

nghttpx: Add PROXY protocol version 2

Fix doc

Always call init_forwarded_for to get the default when source address
in PROXY protocol is ignored.  This ensures that forwarded header
field has the same value as x-forwarded-for.

Add CIFuzz

Fix get_x509_serial for long serial numbers

Fix receiving stream data stall

Enable session_create_idle_stream test, fix errors

Previously, if automatic window update is enabled (which is default),
after window size is set to 0 by
nghttp2_session_set_local_window_size, once the receiving window is
exhausted, even after window size is increased by
nghttp2_session_set_local_window_size, no more data cannot be
received.  This is because nghttp2_session_set_local_window_size does
not submit WINDOW_UPDATE.  It is only triggered when new data arrives
but since window is filled up, no more data cannot be received, thus
dead lock happens.

This commit fixes this issue.  nghttp2_session_set_local_window_size
submits WINDOW_UPDATE if necessary.

https://github.com/curl/curl/issues/4939