fix: panic on assembler source manager mismatch (semver-compat)

[huitseeker]

This is a version of #2987 that is semver-compatible.

[Al-Kindi-0]

Assuming only the semver change is different from #2987

[Al-Kindi-0]

Seems this will need a deeper look by @bitwalker

[bitwalker]

This PR makes some assumptions about how source files are related to modules which are incorrect, so I don't think it makes sense to merge it (or #2987).

I'm not sure this is even the correct way to handle this in general - if you've somehow gotten your source managers mixed up, you want to know exactly where that happened, and a panic is useful for that. If you instead silently drop the source locations, or try to bubble up an Err, you'll lose valuable context about where the wires got crossed.

IMO, this is really a documentation issue related to how SourceManager impls need to be used, both from the caller perspective, and in terms of threading them through internals of the VM or other components.

[bitwalker]

There are two issues with this:

1. Programmatically-constructed modules can absolutely have a backing source file - it just means that the source language was not Miden Assembly (or that the AST was literally constructed by hand for a test, but that's not the important case).
2. Source spans within a Module do not have to come from the same source file, and in fact that is the common case when compiling from Rust source code currently.

[huitseeker]

@bitwalker OK, let's continue the discussion in #2987.