siderophile trait impl output doesn't have full trait paths

[rozbb]

Example: siderophile would output

<rand_pcg::pcg128::Mcg128Xsl64 as RngCore>::next_u64

whereas the label in the crate's callgraph would be

<rand_pcg::pcg128::Mcg128Xsl64 as rand_core::RngCore>::next_u64

This might end up being quite hard to implement, since the tools only looks at source code, and trait path resolution happens at compile time.

[rozbb]

So it doesn't seem like there's an easy way to solve this issue. However, it turns out that stripping all but the last component in the fully-qualified trait path does not increase ambiguity in practice. That is to say, I have yet to find an example of a two distinct paths outputted by siderophile whose fully-qualified path truncations are identical. Even if there were, I think the false positive that this would produce is well worth the complexity that a better solution would likely bring.

All this said, this doesn't technically resolve the issue, so I'll leave it open for the time being. I might be missing something obvious here.