MINOR: sink: change ring buffer "buf0"'s format to "timed"

MINOR: sink: change ring buffer "buf0"'s format to "timed"

This way we now always have the events date which were really missing,
especially when used with traces :

<0>2019-09-26T07:57:25.183845 [00|h2|1|mux_h2.c:3024] receiving H2 HEADERS frame : h2c=0x1ddcad0(B,FRP) h2s=0x1dde9e0(3,HCL)
<0>2019-09-26T07:57:25.183845 [00|h2|4|mux_h2.c:2505] h2c_bck_handle_headers(): entering : h2c=0x1ddcad0(B,FRP) h2s=0x1dde9>
<0>2019-09-26T07:57:25.183846 [00|h2|4|mux_h2.c:4096] h2c_decode_headers(): entering : h2c=0x1ddcad0(B,FRP)
<0>2019-09-26T07:57:25.183847 [00|h2|4|mux_h2.c:4298] h2c_decode_headers(): leaving : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183848 [00|h2|0|mux_h2.c:2559] rcvd H2 response : h2c=0x1ddcad0(B,FRH) : [3] H2 RES: HTTP/2.0 200
<0>2019-09-26T07:57:25.183849 [00|h2|4|mux_h2.c:2560] h2c_bck_handle_headers(): leaving : h2c=0x1ddcad0(B,FRH) h2s=0x1dde9e>
<0>2019-09-26T07:57:25.183849 [00|h2|4|mux_h2.c:2866] h2_process_demux(): no more Rx data : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183849 [00|h2|4|mux_h2.c:3123] h2_process_demux(): notifying stream before switching SID : h2c=0x1dd>
<0>2019-09-26T07:57:25.183850 [00|h2|4|mux_h2.c:1014] h2s_notify_recv(): in : h2c=0x1ddcad0(B,FRH) h2s=0x1dde9e0(3,HCL)
<0>2019-09-26T07:57:25.183850 [00|h2|4|mux_h2.c:3135] h2_process_demux(): leaving : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183851 [00|h2|4|mux_h2.c:3319] h2_send(): entering : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183851 [00|h2|4|mux_h2.c:3145] h2_process_mux(): entering : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183851 [00|h2|4|mux_h2.c:3234] h2_process_mux(): leaving : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183852 [00|h2|4|mux_h2.c:3428] h2_send(): leaving with everything sent : h2c=0x1ddcad0(B,FRH)
<0>2019-09-26T07:57:25.183852 [00|h2|4|mux_h2.c:3319] h2_send(): entering : h2c=0x1ddcad0(B,FRH)

It looks like some format options could finally be separate from the sink,
or maybe enforced. For example we could imagine making the date optional
or its resolution configurable within a same buffer.

Similarly, maybe trace events would like to always emit the date even
on stdout, while traffic logs would prefer not to emit the date in the
ring buffer given that there's already one in the message.