Added: Add collapsible functionality to block forms with expand/collapse all buttons

[drikusroor]

Introduce collapsible functionality to block forms, enhancing user experience with improved visibility and layout. Update styles and documentation to support the new features.

Resolves #1380

Screenshots

Collapsed state

One inline block form expanded

[BeritJanssen]

I like it! As discussed in another channel, I do wonder whether it wouldn't make sense to show the tabular overview of the blocks in a phase at all times, and use the arrow next to "Blocks" to expand/collapse all Block forms instead.

[BeritJanssen]

Looks good! Let's perhaps still look at this together next week? We can of course also merge as is then and refine later though.