Some oddness with views schema

Problem/Motivation

While writing tests for #2879527: Caching issue with the rate widget for users with same role/permissions, these schema errors started cropping up:

1) Drupal\Tests\rate\Functional\RateWidgetTest::testWidgetCaching
Drupal\Core\Config\Schema\SchemaIncompleteException: Schema errors for views.view.rate_results with the following errors: views.view.rate_results:display.default.display_options.fields.value.group_columns variable type is NULL but applied schema class is Drupal\Core\Config\Schema\Sequence, views.view.rate_results:display.default.display_options.fields.value.set_precision missing schema, views.view.rate_results:display.default.display_options.fields.value.precision missing schema, views.view.rate_results:display.default.display_options.fields.value.decimal missing schema, views.view.rate_results:display.default.display_options.fields.value.format_plural missing schema, views.view.rate_results:display.default.display_options.fields.value.format_plural_string missing schema, views.view.rate_results:display.default.display_options.fields.value.prefix missing schema, views.view.rate_results:display.default.display_options.fields.value.suffix missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.set_precision missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.precision missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.decimal missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.format_plural missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.format_plural_string missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.prefix missing schema, views.view.rate_results:display.summary_block.display_options.fields.value.suffix missing schema

The temporary fix is to disable strict schema checking during testing.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes