Rust: Add missing @kind diagnostic query metadata.

Author: geoffw0

rust/ql/src/queries/diagnostics/UnextractedElements.ql

@@ -1,6 +1,7 @@
 /**
  * @name Unextracted Elements
  * @description List all elements that weren't extracted due to unimplemented features or parse errors.
+ * @kind diagnostic
  * @id rust/diagnostics/unextracted-elements
  */
 

rust/ql/src/queries/diagnostics/UnresolvedMacroCalls.ql

@@ -1,6 +1,7 @@
 /**
  * @name Unresolved Macro Calls
  * @description List all macro calls that were not resolved to a target.
+ * @kind diagnostic
  * @id rust/diagnostics/unresolved-macro-calls
  */