floss: Add software rotation advertising feature for legacy controller

Bug: 320461529
Tag: #floss
Test: mmm packages/modules/Bluetooth
Test: NS send/receive on Ext Adv supported device Guybrush/Nipperkin
Test: NS send/receive on legacy device Nami/Sona
Test: bluetooth_Adapter{Adv,LE}Health.all_floss with
      https://crrev.com/c/5319429 on Nami/Sona and Guybrush/Nipperkin
Test: Manually start 2 adv on Nami/Sona and verify suspend behavior
Flag: EXEMPT, Floss-only changes
Change-Id: Ia51f660161aea2db081991eb11827b7bf89b13ac