Provide an auto-fix for compiler error of "Location does not exist"

When a user is creating a snippet, if they haven't created a parameter named location previously, I think it would be great to provide them an autofix to give them

"param location string" at the top of their file in just one click.


Start by tracing how the "Location does not exist" compiler diagnostic is produced while creating a snippet, then identify the editor entry point for one-click fixes. Done means a missing location parameter can be inserted as "param location string" at the top of the file and the diagnostic is resolved.

Written by the indexing model from the issue text.