Make trace tests a shared library. This will facilitate intercepting the GL calls and implementing emulation paths for offscreen redering. Or other EGL/GL features. It does not yet override the GLES loader and uses the shared 'angle_util' loader as it did before. Bug: angleproject:4845 Change-Id: I68806c307f59e1852999299e88dc358781817f12 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2305042 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Manh Nguyen <nguyenmh@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>