setupNewPublicVolume shouldn't run as PublicVolumeTest

If we run setupNewPublicVolume as a test in PublicVolumeTest, we will
call setup() method before running setupNewPublicVolume. setup() method
expects that public volume is already setup, and fails if it is not.
Hence we shouldn't run setupNewPublicVolume device test in the same
class.

Moved setupNewPublicVolume to a new helper class. As
setupNewPublicVolume itself is a setup method, we don't need any setup
methods in this class.

Bug: 158964245
Test: atest CtsPublicVolumeHostTest
Change-Id: I52c33b70cc72dda93a1413cf31aacd4f4af8dc0a
Merged-In: I52c33b70cc72dda93a1413cf31aacd4f4af8dc0a
(cherry picked from commit 0e89756ca48bde9538f6609658289d832667bc27)
5 files changed