HBASE-24144 Update docs from master (addendum)

Bring back documentation from master branch (37b863bd0b), using

```
$ git checkout master -- src/main/asciidoc/
$ git checkout master -- src/site/asciidoc/
```

And then:
 * remove changes from HBASE-23890
   This reverts commit 420e38083f13ebf9ca056d2ee2de2192c23801c7.
 * delete docs re: sync_replication
 * delete docs re: backup
3 files changed