Add dexlayout class filtering

For fixed_up_dexfile, the returned dex only needs to contain a single
class. This CL adds filtering during IR creation to only contain that
class. This speeds up wifi tests from 25s to 15s on marlin.

Bug: 63756964
Bug: 72064989
Test: mm test-art-host-gtest-dexlayout_test -j64
Change-Id: I3648ac886b377d95e33e5b40a63a34c2a9dbde58