tests: kernel: import floating point sharing tests to unified

This is the microkernel version of the FPU sharing test from legacy
modified to  use unified APIs directly.

Jira: ZEP-932

Change-Id: I133a1466ea75201a97c2f8b83c3586fea0a19447
Signed-off-by: Jithu Joseph <jithu.joseph@intel.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>