When running flatland on android-10.0.0_r21 (Pixel 3), libgui's ~EglImage calls
eglTerminate which grabs angle's EGL entry point mutex. The path continues
to libvulkan where eventually another egl call happens (eglDestroyImageKHR) and
it will attempt to take the mutex at the entry point again. So we try to get the
mutex multiple times from the same thread.

Change this mutex to a recursive_mutex to allow for this re-entry of EGL calls

Tests: android-10.0.0_r21/frameworks/native/cmds/flatland
Bug: angleproject:4354
Change-Id: If8a817df45e9f58d5f06884510350e17d7127fa9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2029218
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Cody Northrop <cnorthrop@google.com>