fix(routing): ensure UiState is cleaned up allowing "undefined" for values

[Haroenv]

Summary

Since #5912, we ensure to clean the UiState from empty values, however this was done in a slightly inefficient (looping over values) and unsafe (no checking for undefined) way, as the types implied that RouteState/UiState always is completely given (if you're using TypeScript that's actually the case, you'd get an error returning undefined for refinementList[attribute] for example).

Result

• Simplified the UiState cleaning
• ensure undefined doesn't cause issues
• add new test to each connectors/*/routing where relevant (pushed the tests separately to show they fail with current implementation: https://app.circleci.com/pipelines/github/algolia/instantsearch/9831/workflows/cba7210e-6955-4459-8c82-307d77319955/jobs/47848/tests)

fixes #5954

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[sarahdayan]

Looks correct to me.

As mentioned previously, removeEmptyRefinementsFromUiState looks factorizable, we could have a single util instead of the same function everywhere. I'll let you be the judge of whether we should do it now or keep it for later.

[Haroenv]

The types make it too hard to make factorable, as well as the conditions not being exactly the same anymore. I tried it but will focus again after this is merged/released

[dhayab]

🙇