listcompactions summary with optional group filter

**Is your feature request related to a problem? Please describe.**
In a situation where a backlog of compactions exists and multiple compaction groups are configured, it is difficult to determine which queue is saturated. This prohibits stealing resources from one compaction group to give to another

**Describe the solution you'd like**
I would like to see something like this, given compactions groups small, large
```
# just the summary command
listcompactions --summary

group current queue
small 23 98
large 45 67
```
```
# an equivalent summary command with groups specified
listcompactions --summary --groups=small,large

group current queue
small 23 98
large 45 67
```
```
# a case with a smaller filter
listcompactions --summary --groups=small

group current queue
small 23 98
```
```
# and of course a negative case
listcompactions --summary --groups=medium

no compaction group "medium" exists
```

**Describe alternatives you've considered**
N/A. Basic metadata about compactions should be available via the shell.

**Additional context**
Add any other context or screenshots about the feature request here.

Start by locating the listcompactions command and reading its existing compaction-group handling. Compare the current command behavior with the requested --summary and --groups examples, including the invalid-group case. Done means the command reports current and queued counts per selected group and gives the specified error when a group does not exist.

Written by the indexing model from the issue text.