system: enable kern.msgbuf_show_timestamp by default

[swhite2]

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Is your feature request related to a problem? Please describe.

Over the years parts of the code requiring dmesg parsing have been removed. With 2767713, core shouldn't have edge cases anymore where parsing might fail due to unexpected brackets.

Showing (relative) timestamps is very useful to quickly see the difference in time between kernel messages, aiding debugging. Full timestamps are already available in the system log.

Describe the solution you like

Set kern.msgbuf_show_timestamp to 1 for the default tunables.

Describe alternatives you considered

N/A

Additional context

N/A