Automatically choose a search view, if one is available

Problem/Motivation

When you're adding the simple search form block to, e.g., a Canvas page, you may not know, off the top of your head, what the action URL and get parameter should be. Looking those up is not something new Drupal users will know how to do.

Proposed resolution

In keeping Simple Search Form simple, we should preselect the get parameter if possible.

I propose that we do this in SimpleSearchFormBlock::defaultConfiguration():

1. If Views is enabled, load the first view that has the simple_search_form tag.
2. In that view, find the first exposed search_api_fulltext filter.
3. That filter's identifier should be used as the get parameter.

Remaining tasks

Get maintainer buy-in and implement it with tests.