fix(autocomplete-js): update components with new renderer

[sarahdayan]

This fixes an issue where default components aren't updated with the new createElement when updating the renderer with the Update API.

The issue was caused by the fact that user-provided components are merged last (which allows users to override default components with their own). The consequence is that when updating the options, the "old" default components are therefore merged and override the new ones.

The difficulty is that, because users can technically override default components (provide Highlight, Snippet, etc.), we can't just update default components by name. Therefore, this PR identifies default component with an internal property so that we can only update them and leave user components untouched.

In a future major, it would be simpler to disallow registering components with the same name as default components. It would require less code and remove confusion without removing any important capabilities.

Since this PR was about components, I also implemented the final unimplemented tests.

fixes #934

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Sandbox	Source
@algolia/autocomplete-example-github-repositories-custom-plugin	Configuration
@algolia/autocomplete-example-instantsearch	Configuration
@algolia/autocomplete-example-playground	Configuration
@algolia/autocomplete-example-preview-panel-in-modal	Configuration
@algolia/autocomplete-example-react-renderer	Configuration
@algolia/autocomplete-example-starter-algolia	Configuration
algolia/autocomplete	Configuration
@algolia/autocomplete-example-reshape	Configuration
@algolia/autocomplete-example-vue	Configuration

[dhayab]

Nitpicky suggestion