Small behavioral changes to the unwinder.

- Be a little more lenient when reading the cies/fdes. If next entry data
  winds up incorrect, don't fail, simply stop processing the entries. This
  only applies when reading all of the cies/fdes at once.
- Fail to init an eh_frame with no entries and fallback to assuming the
  eh_frame has no header instead.
- Change the step to always try debug_frame first which has the most
  accurate information.
- Add small unit tests and a couple of offline unit tests to verify
  this behavior.

These changes are needed to support offline unwinding since it depends
on this new behavior.

Bug: 65682279

Test: Ran new unit tests.
Change-Id: I3529f1b0c8e14cd7409494e5de2f3c9e78d0855e
diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index 9389b40..8dae956 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -170,6 +170,8 @@
     data: [
         "tests/files/elf32.xz",
         "tests/files/elf64.xz",
+        "tests/files/offline/bad_eh_frame_hdr_arm64/*",
+        "tests/files/offline/debug_frame_first_x86/*",
         "tests/files/offline/jit_debug_arm32/*",
         "tests/files/offline/jit_debug_x86_32/*",
         "tests/files/offline/gnu_debugdata_arm32/*",