Show a warning if texture is not POT and mipmap is enabled (WebGL 1)

[yaustar]

WebGL 1 doesn't support mipmaps on textures that are not POT. We should show a warning in the inspector to make it clear to the user that this could be a concern:

Eg

"Only WebGL2 supports mipmap generation on non power of two textures in width and height. (E.g. 256 x 256, 512 x 1024). See https://caniuse.com/webgl2 to see current browser support. Expect browsers that only support WebGL1 to render differently."

[yaustar]

Warning should also describe symptoms of what would happen if they aren't POT.

Related forum post: https://forum.playcanvas.com/t/solved-particle-system-textures-appear-pixelated/18787/4

[Maksims]

That is why defaults in assets settings to use PoT - is still important today. And should be disabled only by a developer/artist who is aware of consequences.

[yaustar]

Released with https://github.com/playcanvas/editor/releases/tag/v1.18.21