EGL: Provide color-space support

[MarijnS95]

Closes #1653

Still a few things to do, such as:

• writing a commit message;
• addressing TODOs;
• deciding where to go with EglSurfaceAttributes since it's so easy to get wrong;
• Remove unneeded changes from the example.

[kchibisov]

Do you want me to look into something specific here given that you have it as a draft and have a bunch of debug in the code?

[MarijnS95]

@kchibisov sure the example used to contain a full setup for using EGL HDR color spaces.

As this is "the only" example in glutin I surely feel that shouldn't immediately expose the user to a completely EGL-specific color space setup, especially if we don't even go to lengths to use the right colors in other spaces. I've now dropped that from this PR. If you think we should, I could always reintroduce it as a separate example app (though wouldn't wish to duplicate 90% of the current example... 😅).

This PR still contains some drive-by ideas to make it easier to work with "HDR" surfaces, such as maybe making it more straightforward to create a ConfigTemplateBuilder for different "popular" formats?