Improve support of custom equals in inline classes

- Ensure that typed equals parameter's type is a star projection of
  corresponding inline class

- Make possible to declare typed equals that returns 'Nothing'

- Forbid type parameters in typed equals operator declaration

^KT-54909 fixed
^KT-54910 fixed

compiler/testData/codegen/box/inlineClasses/kt54536.kt

@@ -5,7 +5,7 @@
 
 OPTIONAL_JVM_INLINE_ANNOTATION
 value class A(val x: Int) {
-    fun equals(other: A) = x % 5 == other.x % 5
+    operator fun equals(other: A) = x % 5 == other.x % 5
 }
 
 OPTIONAL_JVM_INLINE_ANNOTATION