Move FloatingTaskInit set up into init method

This makes the code more tidy and consistent with
other classes. Additionally, this allows for easier
annotation of the initialization code.

Bug: 205828770
Test: m LauncherGoResLib
Change-Id: Ib7ecf32cffd5c6af67a4c2095d7cb3e3a2f387e4
(cherry picked from commit f50acd3e)