Add logic for deduplicating in dexlayout

Added logic for dedeplicating blobs, this is only used for code items
in compact dex for now. This currently provides 0.74% code size
reduction on golem

Disabled for now since quickening is fragile and does not play well
with deduped code items currently.

Future work is to fix quickening and dedupe after quickening to get
the most code size savings.

Test: test-art-host-gtest
Bug: 63756964

Change-Id: Iec770d9c1f5171288aca8329a6ca6992375101bc