Bring advice map entries into alignment with other module items in the AST

One thing for follow up after this PR: when pretty-printing a `Module`, we currently do not print out advice map entries (but we do print the constants we generate to represent the keys). Not only does this mean pretty-printed modules don't render 1:1 with the original MASM, but they don't even contain all of the items (i.e. the actual advice map entries). This is basically just an artifact of how we're handling advice map entries today though.

After this PR is merged with the changes I described in my other comment - I think we can refactor things to skip generating the keys as separate `Constant` items, and instead resolve references to the keys (as constants) to the corresponding `AdviceMapEntry` item now that we'll have them in the AST. This would make `AdviceMapEntry` items proper items with associated symbols, and bring advice map entries into alignment with other module items.

_Originally posted by @bitwalker in https://github.com/0xMiden/miden-vm/pull/2563#discussion_r2677187354_

Look at the AST representation of modules in the codebase, focusing on how advice map entries are currently handled versus other module items like constants. Examine the pretty-printing logic for modules to understand why advice map entries are omitted. The goal is to refactor so advice map entries become proper items with symbols, aligning them with other module items and ensuring pretty-printed modules match the original MASM.

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