[DOCFIX] Add master monitoring doc
[DOCFIX] Add master monitoring doc

### What changes are proposed in this pull request?

Add master monitoring doc

### Why are the changes needed?

Add master monitoring doc

### Does this PR introduce any user facing changes?

NA

pr-link: Alluxio/alluxio#16358
change-id: cid-f59c3cd9a8156c88e486a988d54279683f59735a
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