tighten up QUIC "is early data enabled" checks

[kaduk]

In SSL_set_quic_early_data_enabled() we apply a few consistency checks before allowing a state of SSL_EARLY_DATA_CONNECTING to be set. One such check involves inspecting the value of ssl->session->ext.max_early_data and treating a value of 0 as disabling early data. However, per RFC 9001 the max_early_data_size parameter must be exactly 0xffffffff in order to enable 0-RTT for QUIC. AFAICT we should use the more-strict check in this case.