Fix inlay hint bugs (#2895)

* https://github.com/zed-industries/zed/pull/2891

Fixes ranges pointing at incorrect positions inside multi-codepoint
characters

* https://github.com/zed-industries/zed/pull/2890

Defers hint links' document URL resolution into buffer up until the
hover & cmd-click is made by the user.

Release Notes:

- N/A