C#: Add test for assembly attributes in standalone extraction

Author: tamasvajk

csharp/ql/test/library-tests/standalone/assemblyattribute/attr.expected

@@ -0,0 +1 @@
+| standalone.cs:9:2:9:11 | [Attribute1(...)] |

csharp/ql/test/library-tests/standalone/assemblyattribute/attr.ql

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+import csharp
+
+from Attribute a
+where a.getType().getName() = "Attribute1Attribute"
+select a

csharp/ql/test/library-tests/standalone/assemblyattribute/options

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+semmle-extractor-options: --standalone

csharp/ql/test/library-tests/standalone/assemblyattribute/standalone.cs

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+using System;
+
+[assembly: global::Attribute1]
+
+class Attribute1Attribute : Attribute
+{
+}
+
+[Attribute1]
+class A
+{
+}