[Wasm] Do not erase interfaces down to Any type in Wasm signature.

This enables overloading virtual methods with different interface types

compiler/testData/codegen/box/functions/overloadByInterfaceType.kt

@@ -0,0 +1,35 @@
+interface I1 {
+    fun o(): String
+}
+interface I2 {
+    fun k(): String
+}
+
+interface I {
+    fun foo(x: I1): I1
+    fun foo(x: I2): I2
+}
+
+open class C : I {
+    override fun foo(x: I1): I1 = x
+    override fun foo(x: I2): I2 = x
+}
+
+class C2 : C() {
+    override fun foo(x: I1): I1 = x
+    override fun foo(x: I2): I2 = x
+}
+
+fun box(): String {
+    val x: I = C2()
+
+    val o = x.foo(object : I1 {
+        override fun o(): String = "O"
+    }).o()
+
+    val k = x.foo(object : I2 {
+        override fun k(): String = "K"
+    }).k()
+
+    return o + k
+}