[FIR2IR] Make safe call result always nullable

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/ConversionUtils.kt

@@ -389,7 +389,7 @@ fun Fir2IrComponents.createSafeCallConstruction(
     val startOffset = expressionOnNotNull.startOffset
     val endOffset = expressionOnNotNull.endOffset
 
-    val resultType = expressionOnNotNull.type.let { if (isReceiverNullable) it.makeNullable() else it }
+    val resultType = expressionOnNotNull.type.makeNullable()
     return IrBlockImpl(startOffset, endOffset, resultType, IrStatementOrigin.SAFE_CALL).apply {
         statements += receiverVariable
         statements += IrWhenImpl(startOffset, endOffset, resultType).apply {

compiler/testData/codegen/box/classes/kt1018.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 // The IR prduced by FIR implicitly casts `null` of type `Nothing?` to type `Int` instead of `Int?` in `getColumnCount`.
 
 public class StockMarketTableModel() {

compiler/testData/codegen/bytecodeText/nullCheckOptimization/redundantSafeCall.kt

@@ -1,4 +1,3 @@
-// IGNORE_BACKEND_FIR: JVM_IR
 fun test(s: String) = s?.length
 
 // 0 IFNULL

compiler/testData/codegen/bytecodeText/nullCheckOptimization/redundantSafeCall_1_4.kt

@@ -1,5 +1,4 @@
 // !API_VERSION: LATEST
-// IGNORE_BACKEND_FIR: JVM_IR
 
 fun test(s: String) = s?.length
 

compiler/testData/ir/irText/expressions/safeCalls.fir.txt

@@ -158,10 +158,10 @@ FILE fqName:<root> fileName:/safeCalls.kt
   FUN name:box visibility:public modality:FINAL <> () returnType:kotlin.Unit
     BLOCK_BODY
       TYPE_OP type=kotlin.Unit origin=IMPLICIT_COERCION_TO_UNIT typeOperand=kotlin.Unit
-        BLOCK type=kotlin.Int origin=SAFE_CALL
+        BLOCK type=kotlin.Int? origin=SAFE_CALL
           VAR IR_TEMPORARY_VARIABLE name:tmp_5 type:kotlin.Int [val]
             CONST Int type=kotlin.Int value=42
-          WHEN type=kotlin.Int origin=null
+          WHEN type=kotlin.Int? origin=null
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
                 arg0: GET_VAR 'val tmp_5: kotlin.Int [val] declared in <root>.box' type=kotlin.Int origin=null