Fixed a GC bug caused by improper AppImage string fixup.

Previously, AppImage string references were being updated without
properly updating GC metadata.  This patch collects and records the
information necessary to properly patch the references without breaking
the GC.

Bug: 117846779
Bug: 117426394
Test: m test-art-host-gtest
Test: art/test/testrunner/testrunner.py -b --host
Change-Id: I2faac626f7cccf080e7520b87dd117b58c8d64a3