Make route ID optional for @remix-run/testing createRemixStub

[kentcdodds]

Right now, if you don't pass a route.id, both the routes and routeModules properties get undefined keys that override one another for all the routes. TypeScript does't complain about this so we've got two options:

1. default the route ID to the path
2. require a route ID

I prefer option 1.

Here's the code I'm talking about:

[jrestall]

Would be great to see this fixed as useMatches is currently broken for me with @remix-run/testing if a route id isn't explicitly set as it tries to get a route handle here. I hit this very often since remix-validated-form uses useMatches internally.

In remix-stubs I call convertRoutesToDataRoutes via createStaticHandler which automatically sets unique ids for each route and avoids this issue.

So maybe there's an Option 3 where convertRoutesToDataRoutes is used to default all the route ids to their tree path.