Fix `self` and `super` path resolution in block modules
This PR fixes `self` and `super` path resolution with block modules involved.
Previously, we were just going up the module tree count-of-`super` times without considering block modules in the way, and then if we ended up in a block `DefMap`, we adjust "to the containing crate-rooted module". While this seems to work in most real-world cases, we failed to resolve them within peculiar module structures.
`self` and `super` should actually be resolved to the nearest non-block module, and the paths don't necessarily resolve to a crate-rooted module. This PR makes sure every `self` and `super` segment in paths are resolved to a non-block module.
4b06d3c595