Introduce experimental FIR compiler #KT-31265 Fixed

This commit also includes several FIR2IR fixes which helps FIR compiler
to produce normal results

compiler/testData/cli/js/jsExtraHelp.out

@@ -43,6 +43,7 @@ where advanced options include:
   -Xreport-perf              Report detailed performance statistics
   -Xskip-metadata-version-check Load classes with bad metadata version anyway (incl. pre-release classes)
   -Xuse-experimental=<fq.name> Enable, but don't propagate usages of experimental API for marker annotation with the given fully qualified name
+  -Xuse-fir                  Compile using Front-end IR. Warning: this feature is far from being production-ready
   -Xverbose-phases           Be verbose while performing these backend phases
 
 Advanced options are non-standard and may be changed or removed without any notice.

compiler/testData/cli/jvm/extraHelp.out

@@ -107,6 +107,7 @@ where advanced options include:
   -Xreport-perf              Report detailed performance statistics
   -Xskip-metadata-version-check Load classes with bad metadata version anyway (incl. pre-release classes)
   -Xuse-experimental=<fq.name> Enable, but don't propagate usages of experimental API for marker annotation with the given fully qualified name
+  -Xuse-fir                  Compile using Front-end IR. Warning: this feature is far from being production-ready
   -Xverbose-phases           Be verbose while performing these backend phases
 
 Advanced options are non-standard and may be changed or removed without any notice.

compiler/testData/cli/jvm/firHello.args

@@ -0,0 +1,4 @@
+$TESTDATA_DIR$/firHello.kt
+-Xuse-fir
+-d
+$TEMP_DIR$

compiler/testData/cli/jvm/firHello.kt

@@ -0,0 +1,12 @@
+fun box(): String = "OK"
+
+
+class E(s: String) : Exception(s) {
+
+}
+
+fun main(args: Array<String>) {
+    if (box() == "OK") {
+        throw E("Hello")
+    }
+}

compiler/testData/cli/jvm/firHello.out

@@ -0,0 +1 @@
+OK