fix(infiniteHits): fix wrong behavior of showPrevious regarding cachedHits

[eunjae-lee]

Summary

This PR fixes the wrong behavior of showPrevious and showMore because the functions were created at init with cachedHits. It means showPrevious and showMore always have wrong (empty) cachedHits object. Instead, we need to read from cache every time.

fixes algolia/vue-instantsearch#945

Reproduction of the issue from Vue InstantSearch

https://fyn4y.csb.app/?instant_search[page]=4 (https://codesandbox.io/s/instantsearchjs-forked-fyn4y?file=/src/app.js)

• Click "Show more results" and you will see more results.
• Click "Show previous results" and you expect previous hits to be added, but nothing happens.
• Click "Show previous results" again, and it works now.

And the following is the same example with the InstantSearch.js version from this PR and it works fine:

https://tdmbd.csb.app/?instant_search[page]=4 (https://codesandbox.io/s/instantsearchjs-forked-tdmbd?file=/src/app.js)

Result

showPrevious and showMore work correctly.

[codesandbox-ci]

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InstantSearch.js	Configuration