Floats no longer split the inline flow

[nicoburns]

Summary

Split out of #628 per request. Based directly on main with no taffy version change.

Node::is_or_contains_block now returns false for floated nodes: floats are blockified by stylo, but they participate in the inline formatting context as out-of-flow inline boxes, so a span containing a float must not force anonymous-block splitting of its inline context. Fixes WPT css/CSS2/floats/float-in-inline-001/002.html and floats-placement-vertical-001b/001c.xht (in combination with the float support in #625/#628).

Link to Devin session: https://app.devin.ai/sessions/2aa49a15ca484966b5b71922bfd2bb58
Requested by: @nicoburns

WPT results

11 newly passing, 5 newly failing (net +6).

Full diff (16 changed tests)

+ Fail => Pass css/CSS2/abspos/static-inside-float-inside-inline.html
+ Fail => Pass css/CSS2/floats-clear/floats-149.xht
+ Fail => Pass css/CSS2/floats/float-in-inline-001.html
+ Fail => Pass css/CSS2/floats/float-in-inline-002.html
- Pass => Fail css/CSS2/floats/float-nowrap-3.html
+ Fail => Pass css/CSS2/floats/float-nowrap-4.html
- Pass => Fail css/CSS2/floats/float-nowrap-9.html
+ Fail => Pass css/CSS2/floats/float-nowrap-hyphen-rewind-1.html
+ Fail => Pass css/CSS2/floats/floats-placement-vertical-001b.xht
+ Fail => Pass css/CSS2/floats/floats-placement-vertical-001c.xht
- Pass => Fail css/CSS2/normal-flow/block-in-inline-float-between-001.xht
- Pass => Fail css/CSS2/visuren/float-inside-inline-between-blocks-1.html
- Pass => Fail css/css-color/inline-opacity-float-child.html
+ Fail => Pass css/css-ruby/empty-ruby-text-container-float.html
+ Fail => Pass css/css-ruby/ruby-base-container-float.html
+ Fail => Pass css/css-ruby/ruby-float-handling-001.html

_{Generated by the WPT workflow.}

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