tools/testing: Add support for changes to slab for sheaves

The slab changes for sheaves requires more effort in the testing code.
Unite all the kmem_cache work into the tools/include slab header for
both the vma and maple tree testing.

The vma test code also requires importing more #defines to allow for
seamless use of the shared kmem_cache code.

This adds the pthread header to the slab header in the tools directory
to allow for the pthread_mutex in linux.c.

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>