This just gets rid of irrelevant packages in the registry. Looking into
which versions aren't needed would require a deeper pass, so I held off
on that for now.
Before, the tests were in the 300-500ms range and now they take
100-300ms.
This did call to my attention that `unrelated` is misspelled as
`unrelateed` but holding off on fixing that to reduce conflicts.
A comment on killercup/cargo-edit#15 had me worried that `cargo add` was
deleting comments now. It appears that isn't the case for inline
tables.
Standard tables however do delete comments. The work to make sure they
don't conflicts with another need. When changing the source, we delete
the old source fields and append the new which can cause some formatting
to be carried over unnecessarily.
For example, what would normally look like
```toml
cargo-list-test-fixture-dependency = { optional = true, path = "../dependency", version = "0.0.0" }
```
When fixed to preserve comments with my naive solution looks like
```toml
cargo-list-test-fixture-dependency = { optional = true , path = "../dependency", version = "0.0.0" }
```
Note that `optional = true` used to be last, so space separating it and
`}` was kept, now separating it and `,`.
More work will be needed to get this into an ideal state but we can at
least have confidence with inline tables for now.
