EGL: Implement EGL_EXT_image_dma_buf_import_modifiers This reverts Ifbb0a182171646df8161f6f42eafe2a476fea6b2 and implements the previously missing bits. Inspired by the corresponding Vulkan implementation. The extension is used by an upcoming Exo feature which was successfully tested with this patch, see https://chromium-review.googlesource.com/c/chromium/src/+/3857556 Bug: angleproject:7664 Change-Id: I951d1a787e1db3a77b19fcea6186b7aa0a29872f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3904345 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>