[Feature] Preserve source mapping during codegen. Output source map from compilation for tooling like `leo test`.

[mitchmindtree]

🚀 Feature

It would be great if we had some source map available in the compiler output to give nicer feedback from leo test about failing tests.

This doesn't need to be some serialized form or file output - even just an in-memory mapping would be useful as leo tooling invokes the compiler as a library directly in memory anyway.

Motivation

• [Feature] On VM halt (e.g. during leo test) the associated error should provide Leo source context #29035

Implementation

Currently, we track spans nicely throughout type-checking, however we appear to lose this info during code generation. Implementation might look something like:

• Extend AleoStmt variants to include Span (or add a SpannedAleoStmt { span, stmt } struct).
• Modify code generation (compiler/passes/src/code_generation/) to preserve spans.
• Build an instruction/source map during compilation.
• Include the source map in AleoProgram output.