Remove restriction of different Phi values in SelectGenerator

The restriction was blocking select generation and there's no
good reason to have it.

Also took the opportunity to create a robust test suite for
select generation.

Bug: 245535393
Test: dex2oat compiling the app in the bug
Test: art/test/testrunner/testrunner.py --host --64 --optimizing -b
Change-Id: I4d520a0210179ffa05c4536b3936bc3a67990935
5 files changed