Symbolize native debug information for AOTed methods in boot.oat.

The oatdump symbolizer will produce all DWARF information now,
not just the symtab. This allows us to recover almost all native
debug information after the fact, even for non-debuggable oat files.

The main drawback is that non-debuggable oat files do not have
enough stackmaps to provide reasonable line stepping experience.
We might also be missing inlined methods from backtraces.

Change-Id: I73ff6f43a3a0e5a0907af353f74f04e9b0129590