[FIR] Save IR dumps to .ir.txt files instead of .txt in tests

This is needed to avoid clashes between different dumps from different
  handlers

compiler/testData/ir/irText/declarations/provideDelegate/differentReceivers.kt.txt

@@ -19,13 +19,13 @@ operator fun String.getValue(receiver: Any?, p: Any): String {
   return <this>
 }
 
-val testO: String /* by */ 
+val testO: String /* by */
   field = MyClass(value = "O").provideDelegate(host = null, p = ::testO)
   get(): String {
     return #testO$delegate.getValue(receiver = null, p = ::testO)
   }
 
-val testK: String /* by */ 
+val testK: String /* by */
   field = "K"
   get(): String {
     return #testK$delegate.getValue(receiver = null, p = ::testK)
@@ -34,4 +34,3 @@ val testK: String /* by */
 val testOK: String
   field = <get-testO>().plus(other = <get-testK>())
   get
-

compiler/testData/ir/irText/declarations/provideDelegate/local.kt.txt

@@ -40,4 +40,3 @@ fun foo() {
     }
 
 }
-

compiler/testData/ir/irText/declarations/provideDelegate/localDifferentReceivers.kt.txt

@@ -35,4 +35,3 @@ fun box(): String {
   val testOK: String = <get-testO>().plus(other = <get-testK>())
   return testOK
 }
-

compiler/testData/ir/irText/declarations/provideDelegate/member.kt.txt

@@ -39,11 +39,10 @@ class Host {
 
   }
 
-  val testMember: String /* by */ 
+  val testMember: String /* by */
     field = DelegateProvider(value = "OK").provideDelegate(thisRef = <this>, property = Host::testMember)
     get(): String {
       return <this>.#testMember$delegate.getValue(thisRef = <this>, property = Host::testMember)
     }
 
 }
-

compiler/testData/ir/irText/declarations/provideDelegate/memberExtension.kt.txt

@@ -26,7 +26,7 @@ object Host {
     return StringDelegate(s = <this>)
   }
 
-  val String.plusK: String /* by */ 
+  val String.plusK: String /* by */
     field = (<this>, "K").provideDelegate(host = <this>, p = Host::plusK)
     get(): String {
       return <this>.#plusK$delegate.getValue(receiver = <this>, p = Host::plusK)
@@ -37,4 +37,3 @@ object Host {
     get
 
 }
-

compiler/testData/ir/irText/declarations/provideDelegate/topLevel.kt.txt

@@ -32,9 +32,8 @@ class DelegateProvider {
 
 }
 
-val testTopLevel: String /* by */ 
+val testTopLevel: String /* by */
   field = DelegateProvider(value = "OK").provideDelegate(thisRef = null, property = ::testTopLevel)
   get(): String {
     return #testTopLevel$delegate.getValue(thisRef = null, property = ::testTopLevel)
   }
-