floss: prevent device lost when toggle ll privacy

Control ll privacy and own address type with two sysprops. Do the best
effort to keep ll privacy and address policy consistent.

When setting ll privacy and address privacy, read devices in storage.
Only change address policy if there is no LE device connected. This is
to avoid losing previously paired device.

When switching accounts, it is possible to have ll privacy enabled with
own address type public, or ll privacy disabled with own address type
random.

Bug: 319713370
Bug: 338134627
Test: mma -j32
Test: pair le hid and toggle ll privacy in chrome://flags
Test: nearby share
Flag: floss_separate_host_privacy_and_llprivacy
Change-Id: I163ca07363376fbd265312eaa1903a7ff12b1888