lockable: remove QemuLockable from typedefs.h

lockable: remove QemuLockable from typedefs.h

Using QemuLockable almost always requires going through QEMU_MAKE_LOCKABLE().
Therefore, there is little point in having the typedef always present.  Move
it to lockable.h, with only a small adjustment to coroutine.h (which has
a tricky co-dependency with lockable.h due to defining CoMutex *and*
using QemuLockable as a part of the CoQueue API).

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>