floss: Scanner: Remove async and don't call to BTIF when powering off

Generally there's no behavior change, except:
1. Async is removed so we can easily block all BTIF calls when Floss is
   powering off
2. When a pattern monitor is added and the scanner ID is unknown, remove
   it. Previously it just leaks.

The msft commands are not async now and we call them one by one - Always
wait for the complete callback before sending the next one.

Bug: 346656627
Bug: 266752123
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: bluetooth_AdapterAdvMonitor.all_floss on
      WCN3991(qca quirk), RTL8852(rtl quirk), and WCN6856(no quirk)
Test: toggle NearbyShare and FastPair settings, start normal pair,
      verify the correct MSFT/Ext Scan parameter on WCN3991 and RTL8852
Test: verify normal pairing on RTL8822(no MSFT support).
Flag: EXEMPT, Floss-only changes
Change-Id: Iaa5fe05b0959746fb06b3446c36c6f9b6e863b2d