[WASM] Initial infrastructure

- New module ":compiler:backend.wasm"
    - Initial compiler infra (driver, phaser, context)
    - Subset of Wasm AST
    - Skeleton of IR -> Wasm AST
    - Wasm AST -> WAT transformer

- Testing infra

- SpiderMonkey jsshell tool

js/js.translator/testData/wasmBox/number/longHashCode.kt

@@ -0,0 +1,18 @@
+// EXPECTED_REACHABLE_NODES: 1284
+package foo
+
+fun box(): String {
+    var l1: Long = 0x12344478935690
+    var l2: Long = 0x12344478935698
+    var diff: Long = l2 - l1
+    l1 += (diff / 2)
+    l2 -= (diff / 2)
+
+    assertEquals(l1, l2, "When L1 == L2")
+    assertEquals(l1.hashCode(), l2.hashCode(), "L1.hashCode() == L2.hashCode()")
+
+//    var l3: Any = l2
+//    assertEquals(l1.hashCode(), l3.hashCode(), "Any(Long).hashCode()")
+
+    return "OK"
+}