LU-18687 build: consolidate autoconf files

LU-18687 build: consolidate autoconf files

Maintain all of the autoconf files in the same
top-level directory. This mirrors the practices
of other projects (like ZFS) and makes it easier
to find these files.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I6bfdef9032bf768a63292999a6e9369a85240a2b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57933
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Max Wang <wamax@amazon.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>