This change ensures that the following spec language is correctly
implemented:

    the resulting value for RENDERBUFFER_SAMPLES is guaranteed to be
    greater than or equal to samples and no more than the next larger
    sample count supported by the implementation.

For example, if 2, 4, and 8 samples are supported, and if 5 samples are
requested, ANGLE should use 8 samples, and return 8 when
GL_RENDERBUFFER_SAMPLES is queried.

Note: There is a known problem with NVIDIA OpenGL driver that causes
another test to be expected to fail.

Bug: angleproject:2222
Bug: angleproject:4196
Change-Id: I28921badf9568427799b0af347198b5df06c2aaa
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1954444Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Ian Elliott <ianelliott@google.com>