fix(doc): double-reexport can lead to empty module

[asterite]

Description

Problem

Resolves an issue mentioned in AztecProtocol/aztec-packages#20747

Summary

The bug happened in code like this:

mod one {
    pub mod two {
        mod empty {
            pub struct Empty {}
        }
        pub use empty::Empty;
    }
}

pub use one::two;

The way the doc generator works is by checking re-exports, first in submodules:

1. The re-export pub use empty::Empty in two is found. That causes the module two to be changed in a way that pub struct Empty is put inside two. That way two ends up having Empty as a direct children.
2. The re-export pub use one::two is found. Here we do the same, by placing two directly under one.

The problem was that the two that was found was the one before point 1, where it didn't have Empty directly inside it. This happened because of the way we link things (we store them in a map, and when something referenced in that map changed, we didn't update the map accordingly).

Additional Context

1. I also added some Debug derives because otherwise it was kind of hard to debug this
2. It would be nice to have tests for these things but I'm still not sure what's the best way to do that

User Documentation

Check one:

• No user documentation needed.
• Changes in docs/ included in this PR.
• [For Experimental Features] Changes in docs/ to be submitted in a separate PR.

PR Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt on default settings.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Brillig Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: b328bb5	Previous: 7ae460f	Ratio
rollup-tx-merge	0.002 s	0.001 s	2

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Execution Time'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 281f266	Previous: 7ae460f	Ratio
rollup-checkpoint-merge	0.003 s	0.002 s	1.50

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Test Suite Duration'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: b328bb5	Previous: 7ae460f	Ratio
test_report_zkpassport_noir_rsa_	2 s	1 s	2

This comment was automatically generated by workflow using github-action-benchmark.

CC: @TomAFrench