[TP] Refactor util function for instantiating preview fragment

Due to the refactor, we no longer have the newInstance function from
PreviewFragment. Thus we directly instantiate the fragment in the
injector.

Bug: 246968463
Test: manuel testing and it works as before
Change-Id: I223661e2068d6b1c0d32feb45dff8257c6acb6d5
2 files changed