[widgets][spinboxes] Move floating type handling in base class

This allows for code simplification and wider range of type
support.
2 jobs for 211_fix_uint32_spinboxes in 11 minutes and 25 seconds (queued for 8 seconds)
Status Job ID Name Coverage
  Build
passed #163476
docker-build
build_linux_36

00:06:07

passed #163477
macosx
build_macosx_36

00:08:27