Installd: Amend dexopt binder logging

Add an enum for all exit codes used inside dexopt.cpp. Use the dex2oat
return-codes enum for dex2oat exec results. Add a function to map
these enum cases to small string snippets.

Test: mmma frameworks/native/cmds/installd
Test: installd_dexopt_test
Change-Id: I840ecbcaeb3ec1dcd9bd37dff9bdea35202b4731