Revert "Revert "Don't embed the dex code in the oat file if dex is uncompressed.""

Bug: 63920015
Bug: 70854754

Test: oat_writer_test.cc, test.py

Revert was due to userdebug/user differences, which is fixed with:
https://googleplex-android-review.googlesource.com/#/c/platform/build/+/3434091/

This CL also fixes oatdump when the dex code is not in the .vdex file.

This reverts commit e166e676.

Change-Id: Iec924be2ff8f03cf2ebe306e7a0018241f33beb0