Auto merge of #12572 - craftytrickster:10933/shorthands, r=emilio

10933/shorthands

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This implements the serialization of nearly all of the css shorthand properties with the following exceptions:

1. font - this may be implemented correctly, but I am not 100% sure
2. border-radius - I do not know how to implement this, since I am not familiar with how the property works
3. background - this is implemented, but I think that the implementation might be a tiny bit off.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #10933  (github issue number if applicable). Also fixes issue #11448

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- [X] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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