Floss: Only enable page scan when necessary

Currently we always enable page scan upon adapter is on. This causes
some chipset, ex. QCA6174A5, to have performance drop on inquiry
compairing to BlueZ.

Since page scan is used to allow classic device to reconnect, this
CL make Floss to only enable page scan when
1. there is at least 1 non-connected, bonded classic device, or
2. there is at least 1 l2cap or rfcomm socket listening.
This aligns with BlueZ.

Bug: 321519705
Test: manual test
Test: m -j
Tag: #floss
Flag: EXEMPT, Floss only change
Change-Id: I4c42f2e1a4e040b91e94539b5453a3f96f49e5f0