Store resolved Strings for AOT code in .bss.

And do some related refactorings.

Bug: 20323084
Bug: 30627598
Test: Run ART test suite including gcstress on host and Nexus 9.
Test: Run ART test suite including gcstress with baker CC on host and Nexus 9.
Test: Build aosp_mips64-eng.
Change-Id: I1b12c1570fee8e5da490b47f231050142afcbd1e
46 files changed