Extended version of AbstractWriteSignatureTest:

- support multiple expectations in file
- support field signature expectations
- report failures in a more usable format

compiler/testData/writeSignature/declarationSiteVariance/OutInField.kt

@@ -0,0 +1,10 @@
+public val list: List<String> = throw Exception()
+public val mutList: MutableList<String> = throw Exception()
+
+// field: _DefaultPackage::list
+// jvm signature: Ljava/util/List;
+// generic signature: Ljava/util/List<+Ljava/lang/String;>;
+
+// field: _DefaultPackage::mutList
+// jvm signature: Ljava/util/List;
+// generic signature: Ljava/util/List<Ljava/lang/String;>;