Tests, messages and infra for deprecated symbol reporting

compiler/testData/diagnostics/tests/deprecated/imports.kt

@@ -0,0 +1,8 @@
+import <!DEPRECATED_SYMBOL_WITH_MESSAGE!>C<!> as C2
+
+deprecated("obsolete")
+class C {
+    fun use() {}
+}
+
+fun useAlias(c : <!DEPRECATED_SYMBOL_WITH_MESSAGE!>C2<!>) { c.use() }