grass.gunittest: Allow floating point for --min-success argument

[echoix]

Making gunittest accept floating points for --min-success was a one word change, and already worked correctly.

I just followed up by making the percentage displayed with a decimal point, and extracting the repeated nested function as noted in a todo note; they were exactly the same and didn't use anything from the outer context, both were "pure functions", and could've been static functions in other languages.

I tried it out on the vector folder, making sure I didn't compile with some required libraries so some tests would fail (for example, no pdal, so v.in.lidar and v.in.pdal would fail)

For 19/31=0.6129032258064516, using 66.7 fails:

grass --tmp-project XY --exec     python3 -m grass.gunittest.main     --grassdata $HOME --location nc_spm_full_v2alpha2 --location-type nc     --min-success 66.7

For 19/31=0.6129032258064516, using 61.2 passes:

grass --tmp-project XY --exec     python3 -m grass.gunittest.main     --grassdata $HOME --location nc_spm_full_v2alpha2 --location-type nc     --min-success 61.2

[echoix]

@nilason With that will be able to use any fractional percent for the success rate, instead of using a smaller truncated integer

[nilason]

Nice! Good to see the duplicated code go too.