Unnecessarily lost inbounds attribute in GEP

We lose `inbounds` flag of GEPs for different reasons during compilation. My primary intention of opening the issue is to gather information and record them here., since I am not aware of any pressing need to fix this. Keeping `inbounds` could help loop opts in general, but first I want to work with some examples and see how things work in different passes (as opposed to developing a quick fix for a given case).

The issue names GEPs and the inbounds flag but no files, tests, or specific passes. Start by gathering examples of where compilation drops inbounds and comparing behavior across passes; done is a documented record of the cases and their effects, rather than a specified fix.

Written by the indexing model from the issue text.