There are various places where Dolphin created a new KFilePlacesModel which would then query all storage devices and do other expensive work.

It showed up as 37% cost on startup before, now it's 21%

• Verified that only one instance is created and devices are only queried once.
• Verified that places selector in URL bar still works
• Verified that devices are still shown in sidebar
• Adding places still works and is persisted between starts
• Title bar still shows nice place names, e.g. "Home" instead of "username"