Fix horizontal StackPanel width calculation when a child has forceRes…

[carolhmj]

…izeWidth true and fix text block line width calculation rounding.

This deals with two cases:

1. Removes the warning appearing in https://playground.babylonjs.com/#XCPP9Y#17811 when a text block with resizeToFit and forceResizeWidth is inside an horizontal Stack Panel
2. Fixes the layout cycle error and ellipsis wrapping in the example where a text block is sized down and sized up inside an horizontal Stack Panel: https://playground.babylonjs.com/#XCPP9Y#17810

[bjsplat]

Please make sure to label your PR with "bug", "new feature" or "breaking change" label(s).
To prevent this PR from going to the changelog marked it with the "skip changelog" label.

[bjsplat]

Snapshot stored with reference name:
refs/pull/13610/merge

Test environment:
https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13610/merge/index.html

To test a playground add it to the URL, for example:

https://babylonsnapshots.z22.web.core.windows.net/refs/pull/13610/merge/index.html#WGZLGJ#4600

Links to test babylon tools with this snapshot:

https://playground.babylonjs.com/?snapshot=refs/pull/13610/merge
https://sandbox.babylonjs.com/?snapshot=refs/pull/13610/merge
https://gui.babylonjs.com/?snapshot=refs/pull/13610/merge
https://nme.babylonjs.com/?snapshot=refs/pull/13610/merge

To test the snapshot in the playground with a playground ID add it after the snapshot query string:

https://playground.babylonjs.com/?snapshot=refs/pull/13610/merge#BCU1XR#0