Add benchmark for substr_index

[Omega359]

Is your feature request related to a problem or challenge?

As noted in #9864 (comment) there might be some optimization available for the substr_index function so to facilitate that add a benchmark for that function.

Describe the solution you'd like

A new benchmark testing the substr_index function is added and available for use to test the performance of that function and any changes.

Describe alternatives you've considered

No response

Additional context

No response

[Omega359]

take