vc: Improve initial volume control operations

With this patch initial operations contains only VCS mandatory
characteristics plus all CCC subscriptions (this is topic to improvement
as well).

After profile is notified to Java that it is connected, native schedull
remaining reads which is all the VOCS reads.

Bug: 331775328
Test: atest bluetooth_vc_test
Flags: EXEMPT, regression covered with unit tests.
Change-Id: Ic365bf8bdeea49ba33a564e8b5dc18d6509f6a46