Prevent vendors from accessing private VNDK libs

Private VNDK libs are VNDK libs that are only accessible from other VNDK
libs but are inaccessible from vendor libraries. The private VNDK libs
are marked as vendor_available: false.

To enforce this at runtime, the private VNDK libs are excluded from the
list of lib names that links the namespaces.

Also, linker namespaces for vendor processes are modified so that the
VNDK-core and VNDK-SP libs are now loaded in the 'system' namespace and
not in the 'default' namespace.

Bug: 63878960
Test: wahoo devices boot, log does not show any new dlopen error.

Change-Id: Ibfc4f31a97aa6edd7f05cd6177daeb52c165bfeb