SelfDestructTimer should accept seconds

While working on reviewing new Metal pipeline I found it useful to employ "SelfDestructTimer" to compare the startup times, by precisely specifying the profiled time slice.

However, "SelfDestructTimer" currently only allows the time to be expressed in minutes, which is a bit too long if we are trying to focus just on the startup (ex. 5 seconds)

It would be nice to be able to specify the time in seconds.

There are a few ways we could enhance syntax for SelfDestructTimer to do that and keep the current behavior backwards compatible (we can't just outright change the units to seconds):

#1 - use "XXsec" syntax, ex: "SelfDestructTimer=5sec"
#2 - use "XX:XX" syntax, ex: "SelfDestructTimer=0:05"
#3 - use "XX.XX" synatx, ex: "SelfDestructTimer=0.083"

#3 would probably be most direct extension of the current way it works, but also require a bit of math - i.e. 5 seconds --> 5/60 --> 0.083

#2 is the middle ground (might be mistaken for a fraction though)

#1 would probably the easiest for the user and is my preferred way

We might implement all the 3 ways and let the user decide.

This would require CSR