MINOR: h3: use stream error when needed instead of connection

MINOR: h3: use stream error when needed instead of connection

Use a stream error when possible instead of always closing the whole
connection. This requires a new field <err> in h3s structure.

Change slightly the decoding loop to facilitate error propagation. It
will be interrupted as soon as <h3s.err> or <h3c.err> is non null. In
the later case, a CONNECTION_CLOSE is requested through
qcc_emit_cc_app().

For stream error, H3 layer uses qcc_abort_stream_read() coupled with
qcc_reset_stream(). This is in conformance with RFC 9114 which
recommends to use STOP_SENDING + RESET_STREAM emission on stream error.

This commit is part of implementing H3 errors at the stream level.

This should be backported up to 2.7.