Fix hsv to rgb

[devel0]

Make double round ( 1 decimals then 0 decimals ) to overcome lost of precision, see added unit test:

ex. r=0.49999999999999956 would round (r * 255) to 127 instead of expected 128

Note: other cases could require same approach, I only fixed this one.

Note : while library netstandard2.0 its ok, Test and demo frameworks are upgraded from from netcoreapp3.1 to net7 because out of support and generates follow error on unix platforms:

The active test run was aborted. Reason: Test host process crashed : No usable version of libssl was found