[FIR] Add toString() call to expressions in string templates

compiler/testData/codegen/box/primitiveTypes/kt2794.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun box () : String {
    val b = 4.toByte()
    val s = 5.toShort()

compiler/testData/codegen/box/strings/kt3652.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun box(): String {
  var a = 'a'
 

compiler/testData/codegen/box/strings/kt881.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun box() : String {
   val b = 1+1
   if ("$b" != "2") return "fail"

compiler/testData/codegen/box/strings/singleConcatNullable.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun f(s: String?): String {
     return "$s"
 }
@@ -6,4 +5,4 @@ fun f(s: String?): String {
 fun box(): String {
     if (f(null) != "null") return "Fail"
     return "OK"
-}
+}

compiler/testData/codegen/box/when/typeDisjunction.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun foo(s: Any): String {
     val x = when (s) {
         is String -> s
@@ -11,6 +10,3 @@ fun foo(s: Any): String {
 }
 
 fun box() = if (foo("OK") == "OK" && foo(42) == "42" && foo(true) == "") "OK" else "Fail"
-
-
-