Checkbox and Radio Inputs not retaining selected state after form error

Hi @dhruv.mittal,

Pull requests for this project are done on this repository via GitHub: https://github.com/civictheme/monorepo-drupal

There are three parts to this solution:

Update the civictheme_preprocess_fieldset__form_element__civictheme_field__checkboxes and civictheme_preprocess_fieldset__form_element__civictheme_field__radios
In `civictheme_preprocess_fieldset__form_element__civictheme_field__checkboxes`:

We need to change this line:
https://github.com/civictheme/monorepo-drupal/blob/develop/web/themes/co...
And
https://github.com/civictheme/monorepo-drupal/blob/develop/web/themes/co...

to check for `#value` rather than `#default_value`

Update the checkbox preprocessing

We need to change the checkbox preprocessing at: https://github.com/civictheme/monorepo-drupal/blob/develop/web/themes/co... to something like this

 if ($element['#type'] === 'checkbox') {
    $variables['control'][0]['is_checked'] = $element['#value'] ?? FALSE;
    $variables['control'][0]['is_checked'] = (bool) $variables['control'][0]['is_checked'];
  }

Add some behat tests
We need to add some tests ensuring that in error forms retain their values for checkboxes and radios

@dhruv.mittal Could you create the PR from a forked https://github.com/civictheme/monorepo-drupal this way I can review and merge there. Changes from github get pushed up to this repository.

I can review and have behat tests added there.