Update KotlinUnsafeCastOperatorFilter for Kotlin 1.5

[Godin]

Currently execution of any of

mvn clean package -Dkotlin.version=1.5.0-M1
mvn clean package -Dkotlin.version=1.5.0-M2
mvn clean package -Dkotlin.version=1.5.0-RC
mvn clean package -Dkotlin.version=1.5.0

leads to

Failed tests:
  execute_assertions_in_comments(org.jacoco.core.test.validation.kotlin.KotlinUnsafeCastOperatorTest): Instructions (KotlinUnsafeCastOperatorTarget.kt:26) expected:<[FUL]LY_COVERED> but was:<[PART]LY_COVERED>

---

For the following Example.kt

fun f(s: String?): String {
  return s as String
}

Execution of

kotlin/bin/kotlinc Example.kt -d classes
javap -v -p classes/ExampleKt.class

using Kotlin compiler version 1.4 produces

  public static final java.lang.String f(java.lang.String);
    descriptor: (Ljava/lang/String;)Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=4, locals=1, args_size=1
         0: aload_0
         1: dup
         2: ifnonnull     15
         5: new           #10                 // class java/lang/NullPointerException
         8: dup
         9: ldc           #12                 // String null cannot be cast to non-null type kotlin.String
        11: invokespecial #16                 // Method java/lang/NullPointerException."<init>":(Ljava/lang/String;)V
        14: athrow
        15: areturn

whereas using Kotlin compiler version 1.5 produces

  public static final java.lang.String f(java.lang.String);
    descriptor: (Ljava/lang/String;)Ljava/lang/String;
    flags: (0x0019) ACC_PUBLIC, ACC_STATIC, ACC_FINAL
    Code:
      stack=3, locals=1, args_size=1
         0: aload_0
         1: ifnonnull     14
         4: new           #10                 // class java/lang/NullPointerException
         7: dup
         8: ldc           #12                 // String null cannot be cast to non-null type kotlin.String
        10: invokespecial #16                 // Method java/lang/NullPointerException."<init>":(Ljava/lang/String;)V
        13: athrow
        14: aload_0
        15: areturn

and so there is relation with comment that I made in #1143 (comment)
unfortunately bytecode generated by 1.5 is the same as bytecode that both versions generate for

fun f(s: String?): String {
  if (s == null)
    throw NullPointerException("null cannot be cast to non-null type kotlin.String")
  return s
}