LU-930 doc: add static analysis documentation

LU-930 doc: add static analysis documentation

Add more documentation about Clang/LLVM and other
static analysis tools for Lustre. This will make it
easier for other developers to try out various tools.
It will also serve as a place to record best practices
and experiences. Hopefully, this will increase awareness
and usage of these various tools and improve the Lustre
codebase as a result.

This patch also has a few other small doc updates.

Test-Parameters: trivial
Signed-off-by: Timothy Day <timday@amazon.com>
Change-Id: I4bd860775729aaa4ef1ae1cc2cceb6435f3affdd
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/52186
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>