IrFunctionExpression: add 'origin'

This is actually either a LAMBDA or an ANONYMOUS_FUNCTION.
Not quite sure if it's really required, but some tools such as IR-based
decompiler might require this information.

compiler/testData/ir/irText/expressions/badBreakContinue.txt

@@ -16,7 +16,7 @@ FILE fqName:<root> fileName:/badBreakContinue.kt
         condition: CONST Boolean type=kotlin.Boolean value=true
         body: BLOCK type=kotlin.Unit origin=null
           VAR name:lambda type:kotlin.Function0<kotlin.Nothing> [val] 
-            FUN_EXPR type=kotlin.Function0<kotlin.Nothing>
+            FUN_EXPR type=kotlin.Function0<kotlin.Nothing> origin=LAMBDA
               FUN LOCAL_FUNCTION_FOR_LAMBDA name:<anonymous> visibility:local modality:FINAL <> () returnType:kotlin.Nothing 
                 BLOCK_BODY
                   ERROR_EXPR 'Loop not found for break expression: break@L1' type=kotlin.Nothing