reviewed by Stone

EXP-1160 FIX Cannot drag/drop items from inventory into the contents of a prim in latest Mesh build 239475
brought back some old logic for dispatching to child folder as drag and drop fallback

Added comment where sidebar block list is opened.

Made changes per RB feedback.

STORM-638 FIXED "Object Return" didn't return distant objects if the confirmation dialog wasn't suppressed.

Reason: Showing the confirmation dialog resets object selection,
thus there is nothing to derez.

Fix: Save selection until user answers in the confirmation dialog.

I didn't investigate why the bug occurred only for distant object
(must be some internal LLSelectMgr magic).

Addressing review feedback.