[Analysis API] Migrate existing code fragment tests to the new API

analysis/low-level-api-fir/testData/inBlockModification/codeFragments/localClass.kt

@@ -1,3 +1,20 @@
+// MODULE: context
+
+// FILE: context.kt
 fun test() {
-    <caret>Unit
-}
+    <caret_context>Unit
+}
+
+
+// MODULE: main
+// MODULE_KIND: CodeFragment
+
+// FILE: fragment.kt
+// CODE_FRAGMENT_KIND: BLOCK
+class Foo(val x: Int) {
+    fun foo() {
+        <expr>foo()</expr>
+    }
+}
+
+Foo(1)