tests/libqos: embed allocators instead of malloc-ing them separately

tests/libqos: embed allocators instead of malloc-ing them separately

qgraph will embed these objects instead of allocating them in a separate
object.  Expose a new API "generic_alloc_init" and "generic_alloc_destroy"
for that, and rename the existing API with s/init/new/ and s/uninit/free/.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>