[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/badBreakContinue.fir.kt.txt

@@ -1,29 +0,0 @@
-fun test1() {
-  error("") /* ErrorExpression */
-  error("") /* ErrorExpression */
-}
-
-fun test2() {
-  L1@ while (true) { // BLOCK
-    error("") /* ErrorExpression */
-    error("") /* ErrorExpression */
-  }
-}
-
-fun test3() {
-  L1@ while (true) { // BLOCK
-    val lambda: Function0<Nothing> = local fun <anonymous>(): Nothing {
-      break@L1
-      continue@L1
-    }
-
-  }
-}
-
-fun test4() {
-  while (error("") /* ErrorExpression */) { // BLOCK
-  }
-  while (error("") /* ErrorExpression */) { // BLOCK
-  }
-}
-