Extend provider configuration with new options and add ability to filter autocomplete results before rendering

[lukaspawlik]

Description of the Change

This PR contains changes that:

• allow control Autocomplete / Search a bit more by exposing options to configure EP endpoint
• modify autocomplete result before rendering in the list
• fixes some issues with initial state when Autocomplete is also used as default input for classic website search

Alternate Designs

Benefits

Projects will be able to better adjust ElasticPress React integration configuration and UI behaviour.

Possible Drawbacks

Verification Process

Introduced changes were tested on a client project and their behaviour (results links change, initial search term state, modified EP endpoint) was validated correctly.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Changelog Entry

[nicholasio]

Thanks for the PR!