runtime(files): remove coincident lines and reshade vimlogo.svg - #21050

Remove coincident lines and stroke attributes from vimlogo.svg to facilitate printing, vinyl, and document conversion. Re-shade diamond bevels with an NPR shader, preserving original face color.

This is a 98% faithful update of my own 98% faithful update of the Vim logo at [https://www.vim.org/logos.php](https://www.vim.org/logos.php). Coincident lines ("puzzle-piecing") can lead to background color peeking through during rasterization. Because of the consistent use of black outlines, the Vim logo can be drawn without coincident lines (at no point do three colors meet at a corner). I've taken advantage of that to remove coincident edges and any use of stroke attributes. This is now a 100% vector file without any svg-specific attributes that might get misinterpreted in a format conversion. Each color is 1 layer. Black outlines are areas in the black layer that are not covered by higher layers.

I've also made an update to the lighting. The original diamond had what looked to have been warm-to-cool shading which might have been clipped during a file operation. Warm-to-cool shading goes far back with the logo: the 32x32 pixelated size in vim.ico has bright green and definitely blue pixels used for shading.

In my first update, I mimicked the original warm-to-cool shading with a photo-real light setup with yellow lights on a cooler-green surface to meet in the middle at "Vim green". That was OK, I've written a non-photoreal shader for this version that I think does a better job. It's the kind of shader used in technical drawings.

Here are all three: original, first update, this update from left to right. The pull request has an opaque white outline, exactly like the original. I've only made it partially transparent in the comparison to highlight how the geometry changes facilitate a partially transparent outline.

For what it's worth, this is entirely script generated, so "made in Vim".