Treat Tabulator row_contents as real children

[philippjfr]

In the past it was very expensive to have deeply nested layouts so the children of a Tabulator were inserted as roots into the DOM. However with the bokeh 3.x layout engine this is no longer an issue so we now make them proper children which means signals will flow up and down the full tree of views, ensuring that layout and resize events correctly flow. Additionally we also trigger table resize events when a row is expanded.

[codecov]

Codecov Report

Merging #5292 (e19743f) into main (e77da82) will decrease coverage by 57.10%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             main    #5292       +/-   ##
===========================================
- Coverage   80.85%   23.75%   -57.10%     
===========================================
  Files         274      274               
  Lines       39701    39689       -12     
===========================================
- Hits        32100     9430    -22670     
- Misses       7601    30259    +22658     

Flag	Coverage Δ
ui-tests	?
unitexamples-tests	23.75% <ø> (-46.65%)	⬇️

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