Break out bytecodeText/conditions tests into smaller tests for if/while/do-while.

compiler/testData/codegen/bytecodeText/conditions/nullCompareInWhile.kt

@@ -0,0 +1,13 @@
+fun main(p: String?) {
+    // Generates IFNONNULL and GOTO
+    while (p == null) {
+        "loop"
+    }
+}
+
+//0 ICONST_0
+//0 ICONST_1
+//0 ACONST_NULL
+//1 IFNONNULL
+//1 IF
+//1 GOTO