Fix: Identity equality for non Equatable clases.

[madsodgaard]

Use identity for equals methods for types that do not implement Equatable, for example classes:

Swift:

final class MySwiftClass {}

Java:

// Extracted by jextract
public final class MySwiftClass {}

MySwiftClass c1 = MySwiftClass.init();
c1.equals(c1) // would return false before

[ktoso]

A test would be nice to add for these

[ktoso]

Also naming nitpick, this is "is equal" and not "is equatable" we're not checking if the types are equatABLE but if they are :)

[ktoso]

I did the tiny followup and will merge, thank you!

[ktoso]

Nightly Swift seems broken for unrelated reasons rdar://179674933