ps: add times & cputimes format specifiers: cumulative CPU time in seconds

These format specifiers are to time & cputime what etimes is to etime.

Signed-off-by: Sébastien Bigaret <sebastien.bigaret@telecom-bretagne.eu>
1 job for master in 2 minutes and 36 seconds (queued for 5 seconds)
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Status Job ID Name Coverage
  Test
passed #12027523
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00:02:36