[FIR] Check is for impossibility

^KT-58203 Fixed
^KT-62646

compiler/fir/analysis-tests/testData/resolveWithStdlib/contracts/fromSource/good/returnsImplies/safeCall.kt

@@ -13,7 +13,7 @@ fun test1(x: String?): Int? {
 @OptIn(ExperimentalContracts::class)
 fun test2(x: String?): Int? {
     <!WRONG_IMPLIES_CONDITION!>contract {
-        returnsNotNull() implies (x is Boolean)
+        returnsNotNull() implies (<!USELESS_IS_CHECK!>x is Boolean<!>)
     }<!>
 
     return x?.length

compiler/fir/analysis-tests/testData/resolveWithStdlib/intellij/PersistentStateComponent.kt

@@ -20,7 +20,7 @@ fun <T> deserializeAndLoadState(
 ) {}
 
 fun use(beforeRunTask: BeforeRunTask<*>) {
-    if (beforeRunTask is PersistentStateComponent<*>) {
+    if (<!USELESS_IS_CHECK!>beforeRunTask is PersistentStateComponent<*><!>) {
         deserializeAndLoadState(beforeRunTask)
     }
 }

compiler/fir/analysis-tests/testData/resolveWithStdlib/unaryOperators.kt

@@ -14,5 +14,5 @@ fun foo(u: U) {
     val w = +i
 
     val g = "" !in u
-    val f = "" !is Boolean
+    val f = <!USELESS_IS_CHECK!>"" !is Boolean<!>
 }