FIR2IR: correctly set type parameters of property accessors

In particular, we generate different type parameters for
getters & setters here.

compiler/testData/ir/irText/declarations/parameters/propertyAccessors.kt

@@ -1,3 +1,5 @@
+// FIR_IDENTICAL
+
 val test1 get() = 42
 
 var test2 get() = 42; set(value) {}