The `editorSetDecoration` and `editorLinkLine` events are very similar:
They highlight the source line that a (compiler or tool) output line
points to.
However, there are some differences:
* `editorLinkLine` highlights the word at the pointed-to position in
red.
* `editorSetDecoration` moves the cursor on click.
* `editorSetDecoration` is affected by the “highlight linked lines
indefinitely” setting introduced in #4227.
* `editorSetDecoration` does not show the editor’s tab on click if it’s
in the background.
These differences seem unintentional and the result of the duplication
between these events to me, so this PR merges both behaviours as
`editorLinkLine`.
8d0dfcf757