New Issue: Support 'foreach' intents

18500, "e-kayrakli", "Support 'foreach' intents", "2021-09-30T22:29:40Z"

This issue is to capture the general desire towards supporting intents on foreach loops. The foreach loop was added in Implement the `foreach` loop by e-kayrakli · Pull Request #18046 · chapel-lang/chapel · GitHub, and it was added in a way that they are just a specially-marked for loops. This implies lack of intents similar to for. We want to support intents on foreach loops to enable vector-lane-private variables and reductions.

Note that in Should we support task intents on `for` loops? · Issue #17857 · chapel-lang/chapel · GitHub, it looks like we may end up adding for intents, as well. And because foreaches are actually fors in compiler, the implementation for both will have significant overlap.