[ENH] Improve `IdxT=int64_t` testing and support

[Nyrio]

Some primitives are not tested with IdxT=int64_t. Ideally, we should have stress tests for large dimensions that would result in overflows with smaller index types.

Here's an example of why this is important: I encountered an integer overflow in rowNorm with IdxT=int64_t, and found out that the index type wasn't passed to reduced nor in turn to coalescedReduction, thus resulting in the use of the default parameter int. There might be other primitives with the same problem.

[github-actions]

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