misc: Port latest Fyne layout changes

[adamantike]

Specific commits ported, to update the layouts and reduce differences with upstream Fyne code:

• https://github.com/fyne-io/fyne/commit/a9a66f60d2167d7945bcf7718a781335541317c0
• https://github.com/fyne-io/fyne/commit/2cde868904092382ca5f645802ee9d444d8ae6e8
• https://github.com/fyne-io/fyne/commit/99fa7e3a7dc83dd273ad366cc7d336a1e1cee5f6
• https://github.com/fyne-io/fyne/commit/4ea8a5762f1744401ede9f7bd35b3b75890f925e