Fix integer overflow in indexalator pointer logic

[davidwendt]

Description

Fixes integer overflow in the indexalator logic when incrementing/decrementing its data pointer. Any sufficiently large int32 input values used in computing the byte-pointer position causes an overflow when multiplying the value by the byte-width of the underlying index type. For example, this overflow would occur when accessing rows greater than 536,870,912 with an underlying index type of int32 (4-bytes).

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