Update the wasm bootstrap to allow access to the emscripten wrapper to skwasm. (flutter#135723)

Some upcoming engine changes will bind to a function provided by the emscripten JS wrapper around skwasm, rather than just the wasm module itself. This will make sure not to break the benchmarks when those engine changes land. See flutter/engine#46388

Author: eyebrowsoffire

packages/flutter_tools/lib/src/web/file_generators/wasm_bootstrap.dart

@@ -46,7 +46,8 @@ String generateImports(bool isSkwasm) {
         const skwasmInstance = await skwasm();
         window._flutter_skwasmInstance = skwasmInstance;
         resolve({
-          'skwasm': skwasmInstance.asm ?? skwasmInstance.wasmExports,
+          'skwasm': skwasmInstance.wasmExports,
+          'skwasmWrapper': skwasmInstance,
           'ffi': {
             'memory': skwasmInstance.wasmMemory,
           }