[FIR] Create separated FirBlock for loop local val

Refactor FIR builders code for ForExpression

compiler/testData/diagnostics/tests/redeclarations/RedeclaredValsAndVars.fir.kt

@@ -1,3 +1,4 @@
+// FIR_DUMP
 // ISSUE: KT-54405
 
 class A {
@@ -5,7 +6,7 @@ class A {
     operator fun component2() = ""
 }
 
-fun test(b: Boolean) {
+fun testRedeclaration(b: Boolean) {
     val <!REDECLARATION!>y<!> = 1
     val <!REDECLARATION!>y<!> = 2
     val <!REDECLARATION!>`_`<!> = 3
@@ -14,15 +15,16 @@ fun test(b: Boolean) {
         var <!REDECLARATION!>a<!> = 10
         var <!REDECLARATION!>a<!> = 11
     }
+}
+
+fun testNoRedeclaration(list: List<Int>, b: Boolean) {
+    for (el in list) {
+        val el = 42
+    }
     if (b) {
         val z = 3
-        val <!REDECLARATION!>x<!> = 5
-        val <!REDECLARATION!>x<!> = 6
     } else {
         val z = 4
     }
-}
-
-fun test2() {
     val (`_`, _) = A()
 }

compiler/testData/diagnostics/tests/redeclarations/RedeclaredValsAndVars.fir.txt

@@ -0,0 +1,51 @@
+FILE: RedeclaredValsAndVars.fir.kt
+    public final class A : R|kotlin/Any| {
+        public constructor(): R|A| {
+            super<R|kotlin/Any|>()
+        }
+
+        public final operator fun component1(): R|kotlin/Int| {
+            ^component1 Int(1)
+        }
+
+        public final operator fun component2(): R|kotlin/String| {
+            ^component2 String()
+        }
+
+    }
+    public final fun testRedeclaration(b: R|kotlin/Boolean|): R|kotlin/Unit| {
+        lval y: R|kotlin/Int| = Int(1)
+        lval y: R|kotlin/Int| = Int(2)
+        lval _: R|kotlin/Int| = Int(3)
+        lval _: R|kotlin/Int| = Int(4)
+        fun <anonymous>(): R|kotlin/Unit| <inline=Unknown>  {
+            lvar a: R|kotlin/Int| = Int(10)
+            lvar a: R|kotlin/Int| = Int(11)
+        }
+
+    }
+    public final fun testNoRedeclaration(list: R|kotlin/collections/List<kotlin/Int>|, b: R|kotlin/Boolean|): R|kotlin/Unit| {
+         {
+            lval <iterator>: R|kotlin/collections/Iterator<kotlin/Int>| = R|<local>/list|.R|SubstitutionOverride<kotlin/collections/List.iterator: R|kotlin/collections/Iterator<kotlin/Int>|>|()
+            while(R|<local>/<iterator>|.R|SubstitutionOverride<kotlin/collections/Iterator.hasNext: R|kotlin/Boolean|>|()) {
+                lval el: R|kotlin/Int| = R|<local>/<iterator>|.R|SubstitutionOverride<kotlin/collections/Iterator.next: R|kotlin/Int|>|()
+                 {
+                    lval el: R|kotlin/Int| = Int(42)
+                }
+
+            }
+
+        }
+
+        when () {
+            R|<local>/b| ->  {
+                lval z: R|kotlin/Int| = Int(3)
+            }
+            else ->  {
+                lval z: R|kotlin/Int| = Int(4)
+            }
+        }
+
+        lval <destruct>: R|A| = R|/A.A|()
+        lval _: R|kotlin/Int| = R|<local>/<destruct>|.R|/A.component1|()
+    }

compiler/testData/diagnostics/tests/redeclarations/RedeclaredValsAndVars.kt

@@ -1,3 +1,4 @@
+// FIR_DUMP
 // ISSUE: KT-54405
 
 class A {
@@ -5,7 +6,7 @@ class A {
     operator fun component2() = ""
 }
 
-fun test(b: Boolean) {
+fun testRedeclaration(b: Boolean) {
     val <!REDECLARATION!>y<!> = 1
     val <!NAME_SHADOWING, REDECLARATION!>y<!> = 2
     val <!REDECLARATION!>`_`<!> = 3
@@ -14,15 +15,16 @@ fun test(b: Boolean) {
         var <!REDECLARATION!>a<!> = 10
         var <!NAME_SHADOWING, REDECLARATION!>a<!> = 11
     }
+}
+
+fun testNoRedeclaration(list: List<Int>, b: Boolean) {
+    for (el in list) {
+        val <!NAME_SHADOWING!>el<!> = 42
+    }
     if (b) {
         val z = 3
-        val <!REDECLARATION!>x<!> = 5
-        val <!NAME_SHADOWING, REDECLARATION!>x<!> = 6
     } else {
         val z = 4
     }
-}
-
-fun test2() {
     val (`_`, _) = A()
 }

compiler/testData/diagnostics/tests/redeclarations/RedeclaredValsAndVars.txt

@@ -1,7 +1,7 @@
 package
 
-public fun test(/*0*/ b: kotlin.Boolean): kotlin.Unit
-public fun test2(): kotlin.Unit
+public fun testNoRedeclaration(/*0*/ list: kotlin.collections.List<kotlin.Int>, /*1*/ b: kotlin.Boolean): kotlin.Unit
+public fun testRedeclaration(/*0*/ b: kotlin.Boolean): kotlin.Unit
 
 public final class A {
     public constructor A()