[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/regressions/coercionInLoop.kt.txt

@@ -14,4 +14,3 @@ fun box(): String {
   }
   return "OK"
 }
-

compiler/testData/ir/irText/regressions/integerCoercionToT.kt.txt

@@ -39,4 +39,3 @@ class IdType : CPointed {
 fun foo(value: IdType, cv: CInt32VarX<Int>) {
   cv.<set-value><Int>(value = value.<get-value>())
 }
-

compiler/testData/ir/irText/regressions/kt24114.kt.txt

@@ -41,4 +41,3 @@ fun test2(): Int {
     }
   }
 }
-

compiler/testData/ir/irText/regressions/newInference/fixationOrder1.kt.txt

@@ -18,4 +18,3 @@ fun box(): String {
   val x: Inv2<String, Int> = test()
   return "OK"
 }
-

compiler/testData/ir/irText/regressions/typeAliasCtorForGenericClass.kt.txt

@@ -17,4 +17,3 @@ fun bar() {
   val b: A<Int> = A<Int>(q = 2)
   val b2: A<A<Int>> = A<A<Int>>(q = b)
 }
-

compiler/testData/ir/irText/regressions/typeParametersInImplicitCast.kt.txt

@@ -4,4 +4,3 @@ fun <T : Any?> problematic(lss: List<List<T>>): List<T> {
   }
 )
 }
-