Modify apex_available to Bluetooth apex

Bluetooth apex name has changed from com.android.btservices to
com.android.bt. We now need to update the reference in the code.

Updating apex_available in bp and other reference from within the code

Bug: 383863941
Flag: Exempt build infra
Test: m .
Change-Id: I905e2087439229cee18f2ee571947252e1dc1763