The implementation for OES_texture_storage_multisample_2d_array
already exists. This patch just enables the appropriate capability flag
only if the underlying Vulkan ICD supports standardSampleLocations

Bug: angleproject:3583
Tests: angle_end2end_tests
        --gtest_filter="*TextureMultisampleArrayWebGLTest*Vulkan"
    dEQP-GLES31.functional.state_query.internal_format.texture_2d_multisample_array.*
    dEQP-GLES31.functional.state_query.texture_level.texture_2d_multisample_array.*
Change-Id: I2ea89041d9aa8c7d94c9ba732f12528c809807ac
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2416979Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>