[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/lambdas/anonymousFunction.kt.txt

@@ -4,4 +4,3 @@ val anonymous: Function0<Unit>
   }
 
   get
-

compiler/testData/ir/irText/lambdas/destructuringInLambda.kt.txt

@@ -62,5 +62,3 @@ var fn: Function1<A, Int>
 
   get
   set
-
-

compiler/testData/ir/irText/lambdas/extensionLambda.kt.txt

@@ -4,4 +4,3 @@ fun test1(): Int {
   }
 )
 }
-

compiler/testData/ir/irText/lambdas/justLambda.kt.txt

@@ -11,4 +11,3 @@ val test2: Function0<Unit>
   }
 
   get
-

compiler/testData/ir/irText/lambdas/localFunction.kt.txt

@@ -10,4 +10,3 @@ fun outer() {
 
   local()
 }
-

compiler/testData/ir/irText/lambdas/multipleImplicitReceivers.kt.txt

@@ -43,4 +43,3 @@ fun test(fooImpl: IFoo, invokeImpl: IInvoke) {
   }
 ) /*~> Unit */
 }
-

compiler/testData/ir/irText/lambdas/nonLocalReturn.kt.txt

@@ -48,4 +48,3 @@ fun testLrmFoo2(ints: List<Int>) {
   }
 )
 }
-

compiler/testData/ir/irText/lambdas/samAdapter.kt.txt

@@ -5,4 +5,3 @@ fun test1() {
  /*-> Runnable */
   hello.run()
 }
-