sys/metrics: Use "body" log API
i.e., use `log_append_mbuf_body()` rather than
`log_append_mbuf_typed()`.  This removes the need to allocate space in
the mbuf for a log entry header.
@@ -124,9 +124,8 @@ metrics_event_end(struct metrics_event_hdr *hdr)
if (hdr->log) {
om = metrics_get_mbuf();
if (om) {
- os_mbuf_extend(om, sizeof(struct log_entry_hdr));
if (!metrics_event_to_cbor(hdr, om)) {
- log_append_mbuf_typed(hdr->log, hdr->log_module, hdr->log_level,
+ log_append_mbuf_body(hdr->log, hdr->log_module, hdr->log_level,
LOG_ETYPE_CBOR, om);
} else {
ret = -1;
