gettimeofday isn't monotonic

[kpu]

https://github.com/browsermt/mts/blob/41978b4c225138432883a8c1abc98e7a86a31c2c/src/bergamot/request.cpp#L23

NOTES
       The time returned by gettimeofday() is affected by discontinuous jumps in the system time (e.g., if the system
       administrator manually changes the system time).  If you need a monotonically increasing clock, see clock_get‐
       time(2).

Also do you even need a notion of clock time or is a sequence number sufficient to compare ages?

[jerinphilip]

Sequence number should be enough. Should we account for the case of overflow?

[kpu]

64 bits should be enough for everyone!