MMDevice: Unit tests for float property truncation

Turns out all these pass already.

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14602 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd
MMDevice: Simplify float property value rounding

git-svn-id: https://valelab.ucsf.edu/svn/micromanager2/trunk@14603 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd