[FIR Test] Migrate AbstractFirLoadCompiledKotlin to new test infrastructure

Also introduce two different modes for those tests:
- load metadata compiled with K1
- load metadata compiled with K2

compiler/testData/loadJava/compiledKotlin/fromLoadJava/packageLevelObject.fir.txt

@@ -0,0 +1,4 @@
+public final object Bar : R|kotlin/Any| {
+    private constructor(): R|test/Bar|
+
+}