Remove enable from PeriodicAdvertisingPariameters (1/2)

Instead of setting enable to true, one can just pass null
PeriodicAdvertisingParameters and achieve same result when starting the
set.
Passing the "enable" when updating the parameters make no sense, and
might be confusing.
Experience with "timeout" field, which was a part of AdvertiseSettings
show that merging fields that go into different HCI commands can cause
problems during processing, so keep enable as separate field.

Test: manual
Bug: 30622771
Change-Id: Ida02c59eb8433537179b4d22202fe745f8b4bb3e