LU-18162 obdclass: create ldto wrappers and default LU allocator

LU-18162 obdclass: create ldto wrappers and default LU allocator

Wrap calls to ldto_device_* methods with small wrapper functions.
This allows for default behavior to be defined when the ldto_device_*
methods are not defined.

Define a default allocator when ldto_device_alloc and ldto_device_free
are not provided. This will allow many of the simplier OBD devices
to be fully converted to LU devices without as much boilerplate.

Similarly, allow ldto_device_init/fini to be optional.

Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: Iac40138a31a0eef9a2100f958be8e00849301e46
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/58783
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>