Change to new libbacktrace offline functions.

Changes:
- Removes references to libunwind.
- Add enabling of global Elf cache.
- Add new ApkInspector function to get the offset from an apk by name.
- When a map name contains a '!' convert back to a name and offset.
- Initialize global elf cache in OfflineUnwinder constructor.

Bug: 65682279

Test: All unit tests pass.
Change-Id: I303b4beab8270ed2097cd17d91253c321cdc97f1
7 files changed