Collection of UI issues and improvements

[gavento]

Collecting several minor UI issues into one issue. Mostly low priority.

Feel free to add more now but we'll close this once the current issues we decide to address soon are dealt with (others to be discarded or migrated to future or separate issues). Please provide images with the issues.

• Various mis-alignments
  • Spacing of icons
    
• FormatStr is not shortened
  
  • Height-based overflow would also solve this, along with high images etc.
• It would be nice if the vertical bar (and some space around it) was clickable to collapse the block
  
• The preview string can likely be longer
  
• I am no longer certain that smaller observation contexts are that great: they do not take much less space vertically and look weird when expanded (the contents are not smaller)
  • Counter-proposal: make them the same size but 1. make the spacing smaller (so they flow more like "events" should - with simple line spacing), and/or 2. make their color a bit faded (tiiiny bit of transparency?)

[jas-ho]

• copy button for context UID (sorry for the crappy mock-up 🤣 )
  

[jas-ho]

• delete button (with confirmation dialogue) to clean out contexts which are not useful anymore (e.g. failed runs)