Rust: Clean up the test (it turns out a nested UnusedVariable.qlref is not needed) and accept consistency check changes.

Author: geoffw0

rust/ql/test/query-tests/unusedentities/CONSISTENCY/ExtractionConsistency.expected

@@ -1,4 +1,2 @@
 extractionWarning
-| main.rs:512:5:512:28 | macro expansion failed: could not resolve macro 'undefined_macro_call' |
-| main.rs:516:5:516:28 | macro expansion failed: could not resolve macro 'undefined_macro_call' |
-| main.rs:522:13:522:36 | macro expansion failed: could not resolve macro 'undefined_macro_call' |
+| undefined_macros/main.rs:1:1:1:1 | semantic analyzer unavailable (not included as a module) |

rust/ql/test/query-tests/unusedentities/undefined_macros/UnusedVariable.expected

@@ -2,19 +2,19 @@
 // --- undefined macro calls ---
 
 fn undefined_macros1() {
-    let d: u16 = 4;
+    let a: u16;
 
     undefined_macro_call!(d);
 }
 
 fn undefined_macros2() {
     {
-        let a: u16 = 6; // $ MISSING: Alert[rust/unused-variable]
+        let a: u16 = 1; // $ MISSING: Alert[rust/unused-value]
     }
 
     undefined_macro_call!(5);
 
-    let b: u16 = 6; // $ MISSING: Alert[rust/unused-variable]
+    let b: u16; // $ MISSING: Alert[rust/unused-variable]
 }
 
 fn undefined_macros3() {