Better define valid texture uploads with explicit dimensions from TexImageSource objects

[lexaknyazev]

WebGL 2.0 supports explicit dimensions for tex[Sub]Image{2|3}D calls with TexImageSource input data. The spec should define valid ranges for width, height, and depth parameters.

Additionally, all of these entrypoints should be tested with all image source (Image, Canvas, etc) and texture (2D, 3D, ...) types and preferably with all mip levels filled.

Relevant Chromium bug: https://issues.chromium.org/issues/40910322.