Add ES 3.1 check to ValidateBindImageTexture This fixes a crash that occured in the Lego trace when run with an ES 3.0 context. * At the end of each frame it unbinds all the image units using glBindImageTexture, which is an ES 3.1 call. * During validation, we verify things using ANGLE's internals, but they are only set up when the context is >= ES 3.1. * This led to a crash. * The fix is to check the ES context early and bail, which aligns with other entry points. Test: LEGO MEC Bug: b/161716126 Bug: angleproject:4048 Change-Id: I9aee2ee173436f5de5062758a70e0909f6fc9a7f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2462163 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Commit-Queue: Cody Northrop <cnorthrop@google.com>