Add a test PDF and embedder test where a shared form XObject is accessed
by two different annotation paths:
1. Directly (Annotation 1 -> Shared form obj), and
2. Indirectly (Annotation 2 -> Wrapper form obj -> Shared form obj).
The form matrix values incorrectly change when the form XObject is first
accessed directly, then indirectly.
Bug: 475719025
Change-Id: I30439d2585fec3065575b27c7eed2e5c7cd86c7e
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/141130
Commit-Queue: Andy Phan <andyphan@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
