Opening this to track work on BAIN optimizations:

• single propagate_refresh(True) remaining in the code is in Installer_Op.Execute()
• likewise the vast majority of RefreshUI(None) calls that remain are in Installers basher code
• to address those we need to revisit irefresh (thankfully not remotely as complex as before Align irefresh with _AfileInfos.refresh #716) and make sure we properly update the return value to include all and only the changed installers and then use that return value in the UI
• however there is room for optimization also inside the model - namely LowerDict operations take time (CIstr was created for memory efficiency and is not cached) - this deserves an internal issue but there we can start by optimizing in the client and doing some profiling