Display a lot of stats about each database

- The number of entries
- Total size of the keys, values, both
- Overhead of LMDB (total entries size minus disk or pages size)
- Average of the key size, value size, both
- Be able to deserialize the key/value with a program and give the logical length of it i.e. #6.

No files, tests, or entry points are named. Start by locating where each database is displayed in the Rust egui application and how LMDB entries are read; define done as showing the requested counts, size and average statistics, overhead, and deserialized logical lengths.

Written by the indexing model from the issue text.