Retry printer selection in helper

In selectPrinter, the test sometimes receives a StaleObjectException
when trying to click the destination spinner entries.  Try to avoid this
by retrying the object lookup a few times before giving up.

Bug: 392190265
Test: atest CtsPrintTestCases_Presubmit --retry-until-failure 100
Flag: TEST_ONLY
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:f0d663de4d1da399a3ce0da52429fb0729b738d9)
Merged-In: I42155091cba3b0bbe5ac2358126bcb40e3f09443
Change-Id: I42155091cba3b0bbe5ac2358126bcb40e3f09443