Move code item to the data pointer and remove code_item_offset.

This saves 4 bytes on 32bit and 8 bytes on 64bit on ArtMethod.

Also update nterp to directly fetch the code item from the data pointer.

Test: test.py
Bug: 112676029

Change-Id: Ic01f43c7ccf2cbce1ec517478e81362232d36371
16 files changed