impl Eq for RowRef

[Centril]

Description of Changes

Implements Eq + PartialEq for RowRef<'a>.
The impl is unused but will be used in #1107.
Separated out for review purposes.

API and ABI breaking changes

None

Expected complexity level and risk

2, some unsafe, but very local and fairly easy to understand.

[kim]

Seems reasonable.

Are there any actual uses for which the address equality assumption does not hold, and thus the worse performance could come as a surprise?

[Centril]

Are there any actual uses for which the address equality assumption does not hold, and thus the worse performance could come as a surprise?

This impl isn't used in this path currently, but if we used it in find_same_row then we'd end up with committed_table and tx_table having the same layout but not being address equal. This could be solved, if determined to be beneficial, by avoiding a deep clone of row layouts in Table::clone_structure by using Arc<ProductTypeLayout>.