Make Layout 2020/2013 a runtime switch
This change makes the choice between Layout 2020 and Layout
2013 a runtime switch. The main part of the patch is removing all layout
related compile-time flags from the style crate. This makes the style crate a
lot simpler, but now Layout 2020 parses a good deal of features that it doesn't
support (table, vertical-align, etc). The good news is that we plan to add
these features to Layout 2020.
- Compile a single style for both Layout 2020 and Layout 2013
- Remove layout_2020/layout_2013 features
- Update GitHub workflows for single compilation
- Update test results
<!-- Please describe your changes on the following line: -->
---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix#29942
- [x] There are tests for these changes
<!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.-->
<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->
1b00548ac9