LU-9859 libcfs: migrate libcfs_mem.c to lnet/lib-mem.c

LU-9859 libcfs: migrate libcfs_mem.c to lnet/lib-mem.c

Move the libcfs_mem.c code to the LNet core. The prototypes are declared in libcfs_cpu.h
but we don't move them yet since the CPT code depends on the libcfs_mem.c work. This can
end up in a modular cyclic dependency if we move the CPT work right away so limit what is
changed at this point.

Lustre-change: https://review.whamcloud.com/52701
Lustre-commit: 24d515367f44de6b92b453cc9a1c8384e52b5e3f

LU-9859 lnet: move CPT handling to LNet

The CPT work is used for LNet and ptlrpc which is the Lustre LNet
interface. Move this work there and merge the lib-mem.c code as
well since they both work closely together. Move cpt debugfs
handling from libcfs to lnet. Now all remaining debugfs in libcfs
is for debugging.

Lustre-change: https://review.whamcloud.com/52923
Lustre-commit: 7f8cde3b77ada95e8b96dee1996f8d40bd17a538

LU-9859 libcfs: remove workitem.

There are no more users of the "workitem" code so it can be removed.
Lustre uses Linux workqueues instead.

Lustre-change: https://review.whamcloud.com/50462
Lustre-commit: 1782884fa247da0c1400ee6307596b64d6aaa440

Test-Parameters: trivial
Change-Id: I6bf5cd9f20033f988dde1989f0fc5f89ea74b5a2
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/56765
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>