simpleperf: add a python class to wrap objdump.

Refactor the way to find tools.
Add Objdump class to disassemble code, and add test for it.

It is a preparation to show disassemble code in html interface.

Bug: http://b/66914187
Test: run test.py TestTools.
Change-Id: I35bc5de605422c60da2457f793d3904ccb770a67
2 files changed