[Wasm] WasmExport implementation

compiler/testData/codegen/boxWasmJsInterop/wasmExport.kt

@@ -0,0 +1,19 @@
+// TARGET_BACKEND: WASM
+
+import kotlin.wasm.WasmExport
+
+@WasmExport
+fun exportDefaultName(): String = "some string"
+
+fun checkDefaultName(): Int = js("typeof wasmExports.exportDefaultName() === 'object'")
+
+@WasmExport("exportOverriddenName")
+fun exportWithName(): String = "some string"
+
+fun checkOverriddenName(): Int = js("typeof wasmExports.exportOverriddenName() === 'object'")
+
+fun box(): String {
+    if (checkDefaultName() != 1) return "checkDefaultName fail"
+    if (checkOverriddenName() != 1) return "checkOverriddenName fail"
+    return "OK"
+}

compiler/testData/diagnostics/wasmTests/wasmInterop/wasmExport.kt

@@ -0,0 +1,23 @@
+import kotlin.wasm.WasmExport
+
+<!WASM_EXPORT_ON_EXTERNAL_DECLARATION!>@WasmExport("a")
+external fun foo0(): Unit<!>
+
+<!WASM_EXPORT_ON_EXTERNAL_DECLARATION!>@WasmExport("a")
+fun foo1(): Int = js("42")<!>
+
+class C() {
+    <!NESTED_WASM_EXPORT!>@WasmExport("a")
+    fun foo2(): Int = 42<!>
+}
+
+@WasmExport("a")
+fun foo3(): Int = 42
+
+@WasmExport()
+fun foo4(): Int = 42
+
+<!JS_AND_WASM_EXPORTS_ON_SAME_DECLARATION!>@OptIn(kotlin.js.ExperimentalJsExport::class)
+@JsExport()
+@WasmExport()
+fun foo6(): Int = 42<!>