Allows for more wrap modes to TEXTURE_EXTERNAL_OES textures

Test: angle_end2end_tests --gtest_filter=ExternalWrapTest.*
Bug: angleproject:4443
Change-Id: I37bde091b166d7471c13c14fd6b0174136b52ecf
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2103433
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>