Auto merge of #29945 - Loirooriol:fix-float-placement-with-future-margins-2, r=mrobinson

Properly position floats when subsequent boxes collapse margins with containing block (2)

PR #29939 tried to address this but missed various cases.

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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 #29944
- [X] There are tests for these changes

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