[UX] "Add block" dialog: Convert the list to a multi-column table, and add filtering/sorting by the module that provides each block

[klonos]

This issue here is inspired by the challenges we are facing in #2254, and the solution to a similar problem in #6355.

We could consider the following:

• expand the width of the dialog
• add separate columns for:
  • the block title (without prefix)
  • the module providing the block
  • the description
• add another filter by module
• (optional) consider making the default sorting first by module, then by title alphabetically

Could that be an alternative way to solve the UX problem we are trying to address in #2254 by adding prefixes to titles (which can be problematic - read that other issue for details).

[laryn]

I think there are a lot of similarities between the two UIs and I think the clear separation that table columns provide clean up a lot of the muddiness, so I'd be in favor of that.