Add new list compaction-summary command to tempo-cli

[mdisibio]

What this PR does:
This PR adds a new list compaction-summary command to tempo-cli that displays stats grouped by compaction level. I think this will be helpful for understanding and tuning compaction performance. The output looks like this:

Stats by compaction level:

+-----+-------------+--------------------------------+----------------------------+----------------------------+----------------+---------------+
| LVL |   BLOCKS    |             TOTAL              |       SMALLEST BLOCK       |       LARGEST BLOCK        |    EARLIEST    |    LATEST     |
+-----+-------------+--------------------------------+----------------------------+----------------------------+----------------+---------------+
|   0 | 358 (8 %)   | 105,846,286 objects (165 GB)   | 269,834 objects (432 MB)   | 331,026 objects (508 MB)   | 25h43m30s ago  | 1m55s ago     |
|   1 | 98 (2 %)    | 201,021,818 objects (306 GB)   | 546,468 objects (870 MB)   | 2,466,234 objects (3.6 GB) | 37h16m33s ago  | 12m57s ago    |
|   2 | 2352 (55 %) | 13,958,089,963 objects (23 TB) | 2,585,945 objects (3.9 GB) | 7,764,789 objects (14 GB)  | 336h18m51s ago | 53m12s ago    |
|   3 | 1341 (31 %) | 8,993,358,467 objects (15 TB)  | 3,834,660 objects (6.3 GB) | 8,772,996 objects (16 GB)  | 336h3m58s ago  | 2h29m0s ago   |
|   4 | 64 (1 %)    | 473,193,118 objects (798 GB)   | 5,957,494 objects (10 GB)  | 8,271,811 objects (15 GB)  | 335h18m56s ago | 33h28m42s ago |
+-----+-------------+--------------------------------+----------------------------+----------------------------+----------------+---------------+

Which issue(s) this PR fixes:
n/a

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]