doc/rados: Fix and improve formatting in operations/monitoring.rst

doc/rados: Fix and improve formatting in operations/monitoring.rst

Remove bash "$" prompts from a block that should be command output by
changing from promptified block to simple preformatted block.

Use privileged bash prompt consistently for commands requiring
privileges.

Use :ref: instead of link definitions + external relative links to other
docs content.
Add labels for those links in configuration/ceph-conf.rst
operations/monitoring-osd-pg.rst.

Use semantically correct preformatted block types (json and not
javascript / none and not bash).

Remove spaces at end of lines. Change tabs to spaces (retaining columns
but some seem to be jumbled).
Add space between numbers and units.
Change few double spaces after full stop to single space.
Indent more clearly complex multi-line CLI commands.

Use title case consistently for section titles.

Use admonition instead of spelling out "Note:".

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