[Wasm] Add fast path for null in externRefToAny

- Introduce new intrinsics `wasm_ref_cast_null` & `wasm_ref_test_null`.
- Support getting type for immediate from generic argument.
- Remove redundant null check in `tryGetOrSetExternrefBox`.

libraries/stdlib/wasm/internal/kotlin/wasm/internal/ExternalWrapper.kt

@@ -141,13 +141,13 @@ internal fun externRefToAny(ref: ExternalInterfaceType): Any? {
     // TODO rewrite it so to get something like:
     // block {
     //     refAsAnyref
-    //     br_on_cast_fail 0 $kotlin.Any
+    //     br_on_cast_fail null 0 $kotlin.Any
     //     return
     // }
     // If ref is an instance of kotlin class -- return it casted to Any
     val refAsAnyref = ref.externAsWasmAnyref()
-    if (wasm_ref_test<Any>(refAsAnyref)) {
-        return wasm_ref_cast<Any>(refAsAnyref)
+    if (wasm_ref_test_null<Any>(refAsAnyref)) {
+        return wasm_ref_cast_null<Any>(refAsAnyref)
     }
 
     // If we have Null in notNullRef -- return null

libraries/stdlib/wasm/internal/kotlin/wasm/internal/WasmInstructions.kt

@@ -22,9 +22,19 @@ internal fun wasm_unreachable(): Nothing =
 internal fun <To> wasm_ref_cast(a: Any?): To =
     implementedAsIntrinsic
 
+@Suppress("REIFIED_TYPE_PARAMETER_NO_INLINE")
+@WasmOp(WasmOp.REF_CAST_NULL)
+internal fun <reified To> wasm_ref_cast_null(a: Any?): To =
+    implementedAsIntrinsic
+
 internal fun <To> wasm_ref_test(a: Any?): Boolean =
     implementedAsIntrinsic
 
+@Suppress("REIFIED_TYPE_PARAMETER_NO_INLINE")
+@WasmOp(WasmOp.REF_TEST_NULL)
+internal fun <reified To> wasm_ref_test_null(a: Any?): Boolean =
+    implementedAsIntrinsic
+
 internal fun <T> wasm_array_copy(destination: T, destinationIndex: Int, source: T, sourceIndex: Int, length: Int): Unit =
     implementedAsIntrinsic