fix(test_harness): format reported type with g0

[rouson]

fixes #148

[bonachea]

Does not appear to be working as intended. From CI output:

Test-suite run time: 0.10039999999999999E-2 seconds

[bonachea]

To be clear, that might be a reasonably accurate measurement of the running time, but it's unnecessarily difficult to read and includes a bunch of misleadingly meaningless digits that greatly exceed the actual precision of the system clock.

I'd strongly prefer us to ditch the engineering notation entirely and simply print the time in decimal seconds with 3 (or at most 6) decimal places, eg:

Test-suite run time: 0.001 seconds

[bonachea]

CI confirms this now gives results like:

Test-suite run time: .016 seconds

Test-suite run time: 1.603 seconds

etc