Auto merge of #140549 - BoxyUwU:proper_const_norm, r=lcnr

Set groundwork for proper const normalization

r? lcnr

Updates a lot of our normalization/alias infrastructure to be setup to handle mgca aliases and normalization once const items are represented more like aliases than bodies. Inherent associated consts are still super busted, I didn't update the assertions that IACs the right arg setup because that winds up being somewhat involved to do *before* proper support for normalizing const aliases is implemented.

I dont *intend* for this to have any effect on stable. We continue normalizing via ctfe on stable and the codepaths in `project` for consts should only be reachable with mgca or ace.

Author: bors