JVM IR: do not try to optimize casts in TypeOperatorLowering

In case the cast value is used as a receiver to a private method call,
the cast is actually necessary, see KT-48927. Also, this optimization
has backfired once already (see kt48659_identityEqualsWithCastToAny.kt).
It seems that the best way to optimize these casts is not to generate
them in the first place, and/or use bytecode postprocessing.

Apparently the only kind of casts which need to be eliminated are those
which occur on an inline class to its supertype. Otherwise the
unsafe-coerce intrinsic is inserted at the incorrect place, and several
tests fail (uncastInlineClassToAnyAndBack.kt, genericOverride.kt,
classGenericOverride.kt).

 #KT-48927 Fixed

compiler/testData/codegen/box/casts/kt48927_privateMethodOnDerivedCastToBase.kt

@@ -0,0 +1,9 @@
+abstract class Base {
+    private fun test(): String = "OK"
+
+    fun test(d: Derived): String = (d as Base).test()
+}
+
+class Derived : Base()
+
+fun box(): String = Derived().test(Derived())

compiler/testData/codegen/box/inlineClasses/boxReturnValueOnOverride/uncastInlineClassToAnyAndBack.kt

@@ -0,0 +1,14 @@
+inline class X(val x: Any)
+
+interface IFoo<T> {
+    fun foo(): T
+}
+
+class TestX : IFoo<X> {
+    override fun foo(): X = X("OK")
+}
+
+fun box(): String {
+    val t: IFoo<X> = TestX()
+    return ((t.foo() as Any) as X).x.toString()
+}