ART: Clean up patching data in codegens.

Reuse PatchInfo<> for additional architectures and make the
naming more consistent across architectures. Change the
DexFile reference to pointer in preparation for patching
references to the upcoming .data.bimg.rel.ro section.

Update obsolete comments; instead of referencing dex cache
arrays which were used in the past, reference the .bss and
the .data.bimg.rel.ro which shall be used in upcoming CLs.

Test: Rely on TreeHugger.
Change-Id: I03be4c4118918189e55c62105bb594500c6a42c1