! added option to specify the format to display timings

[mihaisebea]

! defaults to nanoseconds ! supports miliseconds and seconds

[mihaisebea]

Thank you very much for taking the time to review my work and for your amazing work.

[MetanoKid]

I've been running some tests and found an issue I had overlooked: any of the time units we select will only display the value as an integer. Say I prefer reasoning in seconds, so I decide to invoke it with s and then go check FunctionCompilations.csv or TemplateInstantiations.csv. Chances are I get a whole lot of 0 in all of the columns and I lose the ability to find out where my build is slow.

What I'd love it to be is:

• Display as many significant decimals as possible.
• Only display decimals when there are any: i.e. when invoking it with ns we wouldn't see any decimals at all.

I'm okay with having:

• Up to 3 or 4 decimals at most: when invoked with s we'd still have data up to milliseconds, which seems enough.
• Display these decimals even when there are no significant values, if that makes the code easier to reason about.

What do you think?