Revert changes to data class equals/hashCode (KT-12330)

This looked like a small and useful change, but caused so many issues
(KT-24474, KT-24790, 30b9caea, and another unreported one -- see the
test update in this commit) that it didn't pay off after all. The
optimization is not that critical for now, as it's only relevant for
data classes where component types have trivial equals/hashCode
implementation, which is not very often

 #KT-12330 Declined

compiler/testData/codegen/bytecodeText/dataClasses/kt12330.kt

@@ -1,4 +0,0 @@
-data class D(val x: List<String>)
-
-// 1 INVOKEVIRTUAL java/lang/Object.hashCode
-// 1 INVOKEVIRTUAL java/lang/Object.equals