PointWithoutAttributesCompliance,
PointCoordRegressionTest,
PointSpriteAlternatingDrawTypes
were failing on Nexus 5X Vulkan, because pointSizeRange is [1,1] there,
and the tests assume they can use point sizes larger than 1.

Fix the tests to check whether the point size they want to use is available.

Note: PointWithoutAttributesCompliance and PointSpriteAlternatingDrawTypes
can actually work with size 1, though they need to calculate center
pixel more accurately. However, looks like there is a bug in Nexus 5X
driver, and no pixels are rendered. The tests do pass on Pixel 2.

Bug: angleproject:2447
Change-Id: I511574b1b11f2516c10209b85f86b3e7052e6686
Reviewed-on: https://chromium-review.googlesource.com/1026979
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>