Dump more dex file data in oatdump

Dump more dex file data in oatdump

Dump some statistics for each dex file along side with strings loaded
from code and dex code bytes.

Sample output:
Cumulative dex file data
Num string ids: 202809
Num method ids: 320464
Num field ids: 162822
Num type ids: 68151
Num class defs: 48061
Unique strings loaded from dex code: 51049
Total strings loaded from dex code: 106651
Number of unique dex code items: 247929
Total number of dex code bytes: 11090574

Added content testing to oat dump test. No significant slowdown.

TEST: test-art-host
Bug: 29462018

Change-Id: I60effd3087d8c427eda4ee26431d5d77165b3939