docs: add workload-tracing document to admin-guide

docs: add workload-tracing document to admin-guide

Add a new section to the admin-guide with information of interest to
application developers and system integrators doing analysis of the
Linux kernel for safety critical applications.

This section will contain documents supporting analysis of kernel
interactions with applications, and key kernel subsystems expectations.

Add a new workload-tracing document to this new section.

Signed-off-by: Shefali Sharma <sshefali021@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Link: https://lore.kernel.org/r/20230131221105.39216-1-skhan@linuxfoundation.org
[jc: tweaked the sphinx formatting a bit]
Signed-off-by: Jonathan Corbet <corbet@lwn.net>