Use `std::path::absolute` instead of `RealFs::canonicalize` to make the
path absolute in `RealFs::trash` as `canonicalize` also resolves
symlinks, so trashing a symlink moved its target to the trash and left
the link dangling.

Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- Not applicable as we don't have a good infrastructure for testing
`RealFs` changes without hitting the machine's actual filesystem and
testing this on `FakeFs` implementation wouldn't prevent a future
regression, unfortunately.
- [x] Performance impact has been considered and is acceptable

Closes #54900 

Release Notes:

- Fixed trashing of symlinks in project panel to actually trash the link
and not its target.