Use better callbacks in LE multi advertising

Right now, LE multi advertising related code uses it's own
implementation of queue on top of static array. Use std::queue, and
base::Callback instead.

Changing function pointers to base::Callback instances is required for
further refactoring, which will turn this code into class.

Bug: 30622771
Test: sl4a BleAdvertiseApiTest ConcurrentBleAdvertisingTest
Change-Id: I839e036c6edb4e19a17def4d68d351296468f88c