Subscribe to chains by genesis hash (#395)

* Handle subscription by hash in the frontend

* Forward-ported backend changes

* Fix unit tests

* Remove unused `chains_by_label`

* fmt

* Updated but failing E2E tests

* subscribe by genesis hash in tests

* fmt

* Copy `BlockHash` instead of returning a ref

* Pin chains by genesisHash

Co-authored-by: James Wilson <james@jsdw.me>

frontend/src/App.tsx

@@ -228,7 +228,7 @@ export default class App extends React.Component<{}, {}> {
     this.chainsCache = stable.inplace(
       Array.from(this.appState.chains.values()),
       (a, b) => {
-        const pinned = comparePinnedChains(a.label, b.label);
+        const pinned = comparePinnedChains(a.genesisHash, b.genesisHash);
 
         if (pinned !== 0) {
           return pinned;