Fix offsetalator when accessing over 268 million rows

[davidwendt]

Description

Fixes an access error when the offsetalator wraps an INT64 offsets column with more than 268,435,455 rows.
The row access type is size_type and is used to calculate the appropriate position within the offsets buffer.
This fix promotes the multiplication to int64 to properly resolve the correct pointer position.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[davidwendt]

/merge