Allow comparing a record to another to collect the differences

```cpp
template <typename Record>
DifferenceView<Record> CollectDifferences(Record const& left, Record const& right) noexcept;
```

where `DifferenceView<T>` holds a reference to the old and new value of each element that has changed from `left` to `right`.

### Example applications

This can be used to easily visualize a before/after state when changing a record in the table.

