Provide Insight into queued compactions

**Is your feature request related to a problem? Please describe.**
When there are lots of compactions running, they get queued up in the tservers? (possibly the CompactionManger) and can only be seen through the Monitor. The only reason an Admin knows that there are compactions queued is in the monitor showing the number in parenthesis.

**Describe the solution you'd like**
Someway for an admin to know the types of the compactions queued and get more information about queued compactions.

**Describe alternatives you've considered**
The Shell provides information about running compactions through the `listcompactions` command and the `fate` command. But the `fate` command will only show user compactions and `listcompactions` will only show running compactions.

Start by comparing the existing Monitor queued-compaction count with the Shell's listcompactions and fate commands. Trace where running and queued compactions are exposed, then define what administrators should see for queued types and details. Done means queued compactions are distinguishable and inspectable rather than only represented by the Monitor's parenthesized count.

Written by the indexing model from the issue text.