feat: add drop key functionality (#6)

Currently, the `Table.Drop()` function is deprecated because it is not implemented yet. Let's add that functionality.

- Adds true drop functionality to the table, through `Table.Drop()`.
- Adds tests for functionality.
- Rewrites fuzz test using `go_fuzz_utils`, to test arbitrary usage patterns.
- Rewrite `bucket` to allow a capacity of zero.
- Rename `Table.Capacity()` to `Table.TotalCapacity()`, to reflect to different between the capacity of the buckets vs. the whole table.
- Enforce 100% mutation test coverage.

Reviewed-on: #6
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

.gremlins.yaml

@@ -4,4 +4,6 @@ unleash:
   timeout-coefficient: 50
   
   workers: 4
-  dry-run: false
+  dry-run: false
+  threshold:
+    efficacy: 1.0