SF: Move pacesetter setting out of SF::onNewFrontInternalDisplay()

As part of trimming down the use of the front internal display concept
throughout SF, move calls to set a new pacesetter to outside of
SF::onNewFrontInternalDisplay().

Flag: com.android.graphics.surfaceflinger.flags.pacesetter_selection
Bug: 255635821
Test: Manually tested on a foldable w/ dumpsys
Change-Id: I6cb008f3ef8b0220923b2f611cb806d7fe325233