Handle modified files where the case of the filename changed on case-insensitive filesystems (#6327)

* Find existing files with case insensitivity if filesystem is case insensitive
* Handle case change in folders
* Optimise to only test file system case sensitivity if the first query found nothing

This limits the overhead to new paths, and adds an extra query for new paths to windows installs

internal/api/resolver_query_find_file.go

@@ -29,7 +29,7 @@ func (r *queryResolver) FindFile(ctx context.Context, id *string, path *string)
 				ret = files[0]
 			}
 		case path != nil:
-			ret, err = qb.FindByPath(ctx, *path)
+			ret, err = qb.FindByPath(ctx, *path, true)
 			if err == nil && ret == nil {
 				return errors.New("file not found")
 			}