Resolve "Cannot search with keyword "merge""

What does this MR do?

Given these files:

$ cat README.md
blah

function
$ cat content
blah:2:blah
$ cat function::foo
blah

When searching for blah, you'd see this before (look at the middle file):

And then after:

Are there points in the code the reviewer needs to double check?

Does the refactor (to only loop over results once) break any existing behaviour?

Why was this MR needed?

There was a bug!

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #41666 (closed).