[Analysis API] Add more ContextCollector tests inspired by dependentCopy

As the on-air analysis is obsolete, related tests are going to be
deleted. Here we add cases not yet covered by 'ContextCollector' tests.

analysis/low-level-api-fir/testData/contextCollector/scripts/insideClassBody.kts

@@ -0,0 +1,5 @@
+class Foo {
+    val x = 0
+
+    <expr>fun foo() {}</expr>
+}