IR: create shared variables for val-variables when needed

This is possible when a lambda's contract guarantees initialization of a
variable.

compiler/testData/codegen/boxInline/contracts/definiteNestedValInitialization.kt

@@ -1,9 +1,9 @@
 // !LANGUAGE: +AllowContractsForCustomFunctions +UseCallsInPlaceEffect +ReadDeserializedContracts
 // !USE_EXPERIMENTAL: kotlin.contracts.ExperimentalContracts
-// IGNORE_BACKEND: JVM_IR
-// IGNORE_BACKEND_MULTI_MODULE: JVM_IR
 // IGNORE_BACKEND: NATIVE
+
 // FILE: 1.kt
+
 package test
 
 import kotlin.contracts.*
@@ -16,8 +16,8 @@ public inline fun <R> myrun(block: () -> R): R {
     return block()
 }
 
-
 // FILE: 2.kt
+
 import test.*
 
 fun box(): String {
@@ -28,4 +28,4 @@ fun box(): String {
         }
     }
     return if (x.inc() == 43) "OK" else "Fail: ${x.inc()}"
-}
+}