fix(layout-grid): "base" span class specificity

[SampsonCrowley]

"base" span classes should not be more specific than device-specific spans.
fixes #2228

also added span-0 classes to implement #2270

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[SampsonCrowley]

@googlebot I signed it!

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[patrickrodee]

Hey Sampson, thanks for your PR! There are more changes in here than just layout-grid fixes (comment changes, decimal changes, etc). Let's revert those and keep this scoped to just the layout-grid fixes.

Let me know if you have any questions!

[SampsonCrowley]

@patrickrodee without those "changes", the system doesn't pass tests because they violate the linting rules

any changes that aren't directly from the grid updates are from running the fix script

I reverted and force pushed up just the grid updates

[chasingduende]

@SampsonCrowley has this effort been abandoned? It seems like the only fix to enable grid spacing/offsets...

[SampsonCrowley]

@chasingduende it wasn't responded to last time I jumped through the hoops to get things merged in, even though it was definitely something that was needed and all tests were passing.

So yeah I haven't looked at it again. Feel free to steal it and claim the credit though