Log wgpu adapter on web

[emilk]

Best reviewed commit-by-commit

What

We previously only logged the wgpu adapter info on native builds. This means we never logged wether or not the web viewer was using WebGL or WebGPU, for instance. With this PR, I now see this in my Arc browser log:

wgpu adapter backend: Gl, device_type: IntegratedGpu, name: "ANGLE (Apple, Apple M1 Pro, OpenGL 4.1)"

I also cleaned up the logging, omitting empty strings.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested app.rerun.io (if applicable)
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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[emilk]

This PR improved the logging in re_renderer, but I also added more logging to the next release of egui-wgpu:

• Log all available wgpu adapters during startup  emilk/egui#3671

[Wumpf]

Related to:

• About menu should display the rendering backend being currently used #4337