doc/mgr: Promptify CLI commands and other formatting fixes

doc/mgr: Promptify CLI commands and other formatting fixes

For CLI commands use the "prompt" block feature consistently.
And remove preceding text block ending of double colon for those where
applicable.
Use the right prompt either # or $ depending if privileges needed.
Indent all CLI commands by 3 spaces which seems to be the existing
majority.
Indent some CLI command output blocks by 4 spaces, same rationale.
Fix paragraphs before CLI commands ending in rendered ".:" or ",:".
Fix some hyperlink missing underscore at end, making it a link
instead of italic text.
Use double backtick inline code formatting for filenames, paths,
command parameters, function name etc.
Fix a typo in example CLI command IP address 0.0.0.0 missing the
last 0.
Fix few example CLI commands missing the "ceph " in the beginning of
the commands.

Signed-off-by: Ville Ojamo <14869000+bluikko@users.noreply.github.com>