FIR IDE: Add ability in test infra to have a "before" file different in

FIR vs FE1.0, and made file naming convention more consistent.

idea/testData/quickfix/replaceWithSafeCall/comment.fir.kt.after

@@ -0,0 +1,7 @@
+// "Replace with safe (?.) call" "true"
+// WITH_RUNTIME
+fun foo(a: String?) {
+    val b = a // comment1
+        // comment2
+        ?.length ?: <caret>
+}