Add new flag to make discovery classic only

Discovery starts and stops LE scanning directly, bypassing the LE
scanning interface and causing COMMAND DISALLOWED errors. This change
introduces a new flag that will make discovery only trigger inquiry.
This requires additional changes from upper layers to also trigger BLE
scanning during discovery to get both.

Bug: 274967984
Tag: #floss
Test: Verified with subsequent changes in Floss
Change-Id: I1a8fb3749327a4d968b6cd7057712ec72a4f98f4