Fix static position of block-level abspos elements in inline layout

[nicoburns]

Summary

Follow-up to #607 (split into two PRs per review; the companion iframe/embed/video dimension-attribute fix is a separate PR).

layout_abspos_child in inline layout used the inline box's line position (ibox.x/ibox.y) as the static position for every abspos element with auto insets. That's only correct for elements whose hypothetical box is inline-level. A div { position: absolute } sibling of an inline replaced element was being placed beside it on the line instead of at the containing block's content-box left edge. The call site now checks original_display.outside() == DisplayOutside::Inline (the display before abspos blockification) and passes an explicit static position:

let static_position = Point {
    x: if is_inline_level { ibox.x } else { container_pb.left },
    y: ibox.y,
};

The RTL inline static-position adjustment also only applies when the box is inline-level.

WPT results

Newly passing vs main (no regressions in css-flexbox, css/CSS2/normal-flow, css/CSS2/positioning):

• css/CSS2/normal-flow/inline-replaced-height-004/007.xht
• css/CSS2/normal-flow/inline-block-replaced-height-004/007.xht

The *-005 variants and absolute-replaced-height-* tests additionally need the percentage dimension attribute mapping from the companion PR.

Link to Devin session: https://app.devin.ai/sessions/0f8547b7fbb949e28e9acdbedb1ca8d2
Requested by: @nicoburns

WPT results

5 newly passing, 1 newly failing (net +4).

Full diff (6 changed tests)

+ Fail => Pass css/CSS2/floats/floats-placement-008.html
+ Fail => Pass css/CSS2/normal-flow/inline-block-replaced-height-004.xht
+ Fail => Pass css/CSS2/normal-flow/inline-block-replaced-height-007.xht
+ Fail => Pass css/CSS2/normal-flow/inline-replaced-height-004.xht
+ Fail => Pass css/CSS2/normal-flow/inline-replaced-height-007.xht
- Pass => Fail css/css-fonts/variations/font-weight-metrics.html

_{Generated by the WPT workflow.}

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