Evaluate use startTs in lock resolution

When a transaction rolls forward or rolls back another transaction, it uses its start timestamp. If a transaction fails, then multiple other transactions could roll its columns forward with different timestamps. Does this matter?

Start by tracing the transaction lock-resolution path for roll-forward and rollback operations, focusing on how the transaction start timestamp is applied to columns. Investigate the failed-transaction scenario with multiple resolvers using different timestamps, then determine whether it can produce incorrect state and what tests or behavior would establish that it is fixed.

Written by the indexing model from the issue text.