This adds general overview documentation for data tiers,
the data tiers specific node roles, and their application in
ILM.
Co-authored-by: Lee Hinman <dakrone@users.noreply.github.com>
Co-authored-by: debadair <debadair@elastic.co>
(cherry picked from commit d588cab747)
Signed-off-by: Andrei Dan <andrei.dan@elastic.co>
Co-authored-by: Lee Hinman <dakrone@users.noreply.github.com>
Co-authored-by: debadair <debadair@elastic.co>
