As the script depends on python3, let's put it into a new
osmo-remsim-apitool package.
As we're installing the tool system-wide, rename it from
remsim-apitool.py to osmo-remsim-apitool.
Closes: OS#5612
Change-Id: I11d779f66833b5294ffeb422ce6b2a705719a899