Add dangling comment handling to dictionary key-value pairs (#7495)
## Summary
This PR fixes a formatting instability by changing the comment handling
around the `:` in a dictionary to mirror that of the `:` in a lambda: we
treat comments around the `:` as dangling, then format them after the
`:`.
Closes https://github.com/astral-sh/ruff/issues/7458.
## Test Plan
`cargo test`
No change in similarity.
Before:
| project | similarity index | total files | changed files |
|--------------|------------------:|------------------:|------------------:|
| cpython | 0.76083 | 1789 | 1631 |
| django | 0.99983 | 2760 | 36 |
| transformers | 0.99956 | 2587 | 404 |
| twine | 1.00000 | 33 | 0 |
| typeshed | 0.99983 | 3496 | 18 |
| warehouse | 0.99929 | 648 | 16 |
| zulip | 0.99969 | 1437 | 21 |
After:
| project | similarity index | total files | changed files |
|--------------|------------------:|------------------:|------------------:|
| cpython | 0.76083 | 1789 | 1631 |
| django | 0.99983 | 2760 | 36 |
| transformers | 0.99956 | 2587 | 404 |
| twine | 1.00000 | 33 | 0 |
| typeshed | 0.99983 | 3496 | 18 |
| warehouse | 0.99929 | 648 | 16 |
| zulip | 0.99969 | 1437 | 21 |