Offset table row backgrounds and collapsed borders by table border/padding

[nicoburns]

Summary

Fixes misaligned table painting visible on https://blitz.is/status/wpt/css/CSS2/floats: white first-column cell backgrounds didn't line up with rows and the coloured <tr> backgrounds bled through the collapsed-border gutters.

Table cells are laid out inside the table's content box (offset by the table-level border/padding that build_table_context synthesizes — in border-collapse: collapse mode the table border is set to the cell border width), but draw_table_row_backgrounds and draw_table_borders painted their rects starting at the border-box origin (0, 0). Every row-background rect and inner gutter fill was therefore shifted up/left by one border width relative to the cells:

before: row k bg at   y = Σ sizes/gutters            (misses border.top)
after:  row k bg at   y = border.top + padding.top + Σ sizes/gutters

Both functions now resolve table.style.border/padding (via ResolveOrZero) and offset all rects by them. The outer borders in draw_table_borders are also now drawn from the table's own resolved border widths spanning the full border-box (previously they used the first cell's border width and only spanned inner_width/inner_height, leaving the corners uncovered and sitting one border width too high/left on the bottom/right edges).

Verified against the live page and a minimal repro: row backgrounds, cell backgrounds, and collapsed borders now align.

Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/65672de3b7ef45f88c8a46c16e1ac8b2
Requested by: @nicoburns

WPT results

3 newly passing, 0 newly failing (net +3).

Full diff (3 changed tests)

+ Fail => Pass css/CSS2/tables/border-collapse-dynamic-table-003.xht
+ Fail => Pass css/CSS2/visufx/overflow-applies-to-001.xht
+ Fail => Pass css/css-backgrounds/ttwf-reftest-borderRadius.html

_{Generated by the WPT workflow.}

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