Type checking fix: Restrict the keys / values for ArtifactLocation and centralize the common ones

pkg/qldbstore/interfaces.go

@@ -8,6 +8,7 @@ type CodeQLDatabaseLocation struct {
 	// `data` is a map of key-value pairs that describe the location of the database.
 	// For example, a simple key-value pair could be "path" -> "/path/to/database.zip".
 	// A more complex implementation could be "bucket" -> "example", "key" -> "unique_identifier".
+	// XX: static types
 	data map[string]string
 }