lnc+util: assign WASM callbacks to a namespaced scope

[jamaljsr]

This PR updates the LNC class to no longer use the JS global object for the callbacks from the WASM client. The callbacks functions will now be nested under an object using the namespace as a name. So if the app uses new LNC({ namespace: 'myapp' });, the callbacks will be created on the global.myapp object instead of previously being on global.

This depends on https://github.com/lightninglabs/lightning-node-connect/pull/72 which has been merged into the master branch.

Steps to test with the kitchen-sink demo:

1. Clone the lightning-node-connect repo
2. Run make wasm to produce the WASM binary
3. Checkout this PR branch in the lnc-web repo
4. Copy lightning-node-connect/example/wasm-client.wasm into lnc-web/demos/kitchen-sink/public/
5. Update kitchen-sink/src/App.js to use the new WASM binary and your own pairing phrase and namespace

     const lnc = new LNC({
        namespace: 'myapp',
        pairingPhrase: 'iron boss window awful list bag crucial mixture useless piano',
        password: 'Dm9lfaWmo92Q#m9f',
        wasmClientCode: '/lnc-5903579.wasm',
     });

6. Ensure that the kitchen-sink demo is using this branch of the lnc-web code. Then start the app

   $ cd demos/kitchen-sink/
   $ yarn
   $ yarn add ../..
   $ yarn start

7. In the browser, click on the "Connect" button and confirm the connection is successful by clicking on getInfo
8. In the console, confirm that window.onLocalPrivCreate is undefined and that typeof window.myapp.onLocalPrivCreate is function

Note: This PR also fixes an issue in the credentialStore where it was overwriting the data on every page reload in the kitchen-sink demo. This was due to the password being provided in the constructor.

[jamaljsr]

but for some reason when I tried with 4 nodes at once the last node was still being silently dropped. 🤔

I'm not sure why that's happening. Can you confirm that the callbacks for all four connections are all being called? It should be logged in the console. You can also check that the local/remote keys are set for all 4 nodes in localStorage.

[itsrachelfish]

@jamaljsr after doing some further testing it looks like we might be hitting some kind of rate limiting / DOS protection in Firefox.

You can see in this first screenshot (firefox) only three of the WASM binaries are loaded -

However in Chrome it works fine with 4 simultaneous connections -

[jamaljsr]

@jamaljsr after doing some further testing it looks like we might be hitting some kind of rate limiting / DOS protection in Firefox.

Interesting. I was not aware of that limitation, but it's definitely something we need to consider when handling multiple WASM instances. I wonder how the other browsers (Safari, Edge, Brave) handle it. Also mobile browsers may have strict limitations as well.