[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/expressions/funInterface/arrayAsVarargAfterSamArgument_fi.kt.txt

@@ -1,5 +1,5 @@
 fun interface IRunnable {
-  abstract fun run() 
+  abstract fun run()
 
 }
 
@@ -53,4 +53,3 @@ fun test(fn: Function0<Unit>, r: IRunnable, s: String, arr: Array<String>) {
   }
  /*-> IRunnable */, s = [*arr])
 }
-

compiler/testData/ir/irText/expressions/funInterface/basicFunInterfaceConversion.kt.txt

@@ -1,5 +1,5 @@
 fun interface Foo {
-  abstract fun invoke(): String 
+  abstract fun invoke(): String
 
 }
 
@@ -13,4 +13,3 @@ fun test(): String {
   }
  /*-> Foo */)
 }
-

compiler/testData/ir/irText/expressions/funInterface/castFromAny.kt.txt

@@ -1,5 +1,5 @@
 fun interface KRunnable {
-  abstract fun invoke() 
+  abstract fun invoke()
 
 }
 
@@ -7,4 +7,3 @@ fun test(a: Any?) {
   a as Function0<Unit> /*~> Unit */
   a /*as Function0<Unit> */ /*-> KRunnable */.invoke()
 }
-

compiler/testData/ir/irText/expressions/funInterface/partialSam.kt.txt

@@ -1,5 +1,5 @@
 fun interface Fn<T : Any?, R : Any?> {
-  abstract fun run(s: String, i: Int, t: T): R 
+  abstract fun run(s: String, i: Int, t: T): R
 
 }
 
@@ -64,4 +64,3 @@ fun test(j: J) {
   }
  /*-> Fn<String, Int> */, f2 = <get-fis>()) /*~> Unit */
 }
-

compiler/testData/ir/irText/expressions/funInterface/samConversionInVarargs.kt.txt

@@ -1,5 +1,5 @@
 fun interface IFoo {
-  abstract fun foo(i: Int) 
+  abstract fun foo(i: Int)
 
 }
 
@@ -39,4 +39,3 @@ fun testAdaptedCR() {
     ::withVarargOfInt /*-> IFoo */
   }])
 }
-

compiler/testData/ir/irText/expressions/funInterface/samConversionInVarargsMixed.kt.txt

@@ -1,5 +1,5 @@
 fun interface MyRunnable {
-  abstract fun run() 
+  abstract fun run()
 
 }
 
@@ -16,4 +16,3 @@ fun test(a: Any, r: MyRunnable) {
 
 fun foo(vararg rs: MyRunnable) {
 }
-

compiler/testData/ir/irText/expressions/funInterface/samConversionOnCallableReference.kt.txt

@@ -1,5 +1,5 @@
 fun interface KRunnable {
-  abstract fun run() 
+  abstract fun run()
 
 }
 
@@ -40,4 +40,3 @@ fun testSamConversionOnAdapted() {
     ::foo1 /*-> KRunnable */
   })
 }
-

compiler/testData/ir/irText/expressions/funInterface/samConversionsWithSmartCasts.kt.txt

@@ -1,5 +1,5 @@
 fun interface KRunnable {
-  abstract fun run() 
+  abstract fun run()
 
 }
 
@@ -75,4 +75,3 @@ fun test8(a: Function0<Unit>) {
 fun test9() {
   run1(r = ::test9 /*-> KRunnable */)
 }
-