floss: Wire set_scan_mode to Rust layer

The BTIF API is refactored by https://r.android.com/3130657 and this
patch follows the Android changes.

Bug: 310147428
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: bluetooth_AdapterSAHealth.sa_basic_test.floss
Test: bluetooth_AdapterCLHealth.cl_adapter_pairing_test.floss
Test: bluetooth_AdapterSRHealth.sr_while_advertising.floss
Test: manual PhoneHub / SmartLock / NearbyShare HighVis / Fast Pair
Test: manual verified a short discoverable timeout correctly reset the
      scan mode after suspend/resume
Flag: EXEMPT, Floss-only changes
Change-Id: I0c8aaaa78429174f2b3858d35ee07023555ab043