[ty] show final search path instead of "and 1 more paths" (#22776)
## Summary
If there are six search paths, five are attached as subdiagnostic of
unresolved imports but the sixth is by default hidden and replaced by
"... and 1 more paths. Run with `-v` to see all paths."
```
info: Searched in the following paths during module resolution:
info: 1. <temp_dir>/extra1 (extra search path specified on the CLI or in your config file)
info: 2. <temp_dir>/extra2 (extra search path specified on the CLI or in your config file)
info: 3. <temp_dir>/extra3 (extra search path specified on the CLI or in your config file)
info: 4. <temp_dir>/extra4 (extra search path specified on the CLI or in your config file)
info: 5. <temp_dir>/ (first-party code)
info: ... and 1 more paths. Run with `-v` to see all paths.
```
By hiding a single path this truncation does not shorten the output but
still requires the user to rerun ty. We can just include the final
search path instead.
The subdiagnostic "and 1 more paths" isn't helpful - we can show the
hidden path instead (and still have the same number of subdiagnistics).
```
info: Searched in the following paths during module resolution:
info: 1. <temp_dir>/extra1 (extra search path specified on the CLI or in your config file)
info: 2. <temp_dir>/extra2 (extra search path specified on the CLI or in your config file)
info: 3. <temp_dir>/extra3 (extra search path specified on the CLI or in your config file)
info: 4. <temp_dir>/extra4 (extra search path specified on the CLI or in your config file)
info: 5. <temp_dir>/ (first-party code)
info: 6. vendored://stdlib (stdlib typeshed stubs vendored by ty)
```
## Test Plan
* cargo test extended
* manual invocation (with the configuration that prompted me to propose
this change).
