MINOR: quic: refactor frame parsing

MINOR: quic: refactor frame parsing

This patch refactors parsing in QUIC frame module. Function
qc_parse_frm() has been splitted in three :
* qc_parse_frm_type()
* qc_parse_frm_pkt()
* qc_parse_frm_payload()

No functional change. The main objective of this patch is to facilitate
a QMux implementation. One of the gain is the ability to manipulate QUIC
frames without any reference to a QUIC packet as it is irrelevant for
QMux. Also, quic_set_connection_close() calls are extracted as this
relies on qc type. The caller is now responsible to set the required
error code.