Add column_start and column_end to file_location

What does this MR do?

Adds optional column_start and column_end properties to details.file_location for the second iteration of Code Flows.
Those fields should either both exist or neither.
For example, here the source and the first propagation node share the same line number, but differ in column_start and column_end. The addition of columns will allow us to display the flow more accurately.

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab/-/issues/461779+s
https://gitlab.com/gitlab-org/gitlab/-/issues/458062#note_1901685296

Checklist

• Ensure changes can be built upon without requiring a breaking change, see Building for Extensibility.
• Review and add/update tests for this feature/bug.
• Add an entry to the CHANGELOG if required, with the appropriate version. See Classifying Changes.
• Assign the MR to the appropriate person/people for review.