IR: Lower shared variables in enum entries (KT-46605)

compiler/testData/codegen/box/enum/kt46605.kt

@@ -0,0 +1,17 @@
+fun call(f: () -> Unit) {
+    f()
+}
+
+enum class E(val f: () -> String) {
+    A({
+          var value = "Fail"
+          call {
+              value = "OK"
+          }
+          value
+    })
+}
+
+fun box(): String {
+    return E.A.f()
+}