doc/rados: Fix minor issues, improvements in health-checks.rst (3 of x)

doc/rados: Fix minor issues, improvements in health-checks.rst (3 of x)

Also changed in monitoring.rst:
- Add label for link.
- Linkify mention of health checks.

Fix "bluestore bluefs" admin-socket commands after #38437.

Use ":confval:" instead of simple inline literal text for config values.

Use a privileged prompt for CLI command examples requiring privileges.

Trim section title syntax underline.

Use admonition instead of emphasis on the whole paragraph.

Attempt to improve language in a few sentences.

Use double backticks consistently for literals.

Linkify, adding a label in the destination if necessary:
- Muting health checks
- BlueStore migration

Capitalize Ceph, BlueStore, RADOS.

Add paragraph linking to more info on the "ceph df" command.

Use DB or DB device instead of literal db.

Add unordered list formatting to what was being rendered as single paragraph.

Use ":program:" for linking to ceph-bluestore-tool.

Change few last double spaces after full stop to a single space.

Use code-block paragraphs instead of inline literals where appropriate.

Add missing word "is".

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