## Summary

Fixes elastic#198754

Restore previous removed tests when performing the refactor.
The new tests take advantage of the new architecture to be more modular
and close to the logic modules.

The `data_loader` tests are not just covering the re-render logic but
also some `expression_params` logic, who in the past have proven to be
the source of some bugs: specifically the tests will check that the
params are correctly passed to the params logic and then stored
correctly in the observable.

New mocks take advantage of the plain initializers to build some of the
API, that will make it in sync with the actual implementation for future
maintenance.

### Checklist

Check the PR satisfies following conditions.

- [x] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios

---------

Co-authored-by: kibanamachine <42973632+kibanamachine@users.noreply.github.com>
Co-authored-by: Marta Bondyra <4283304+mbondyra@users.noreply.github.com>
(cherry picked from commit 41950c2)

# Conflicts:
#	x-pack/platform/plugins/shared/lens/public/react_embeddable/mocks/index.tsx