PluginOperationsProviderPluginManagerTrait requires array access to plugin definitions

Problem/Motivation

\Drupal\plugin\Plugin\OperationsProviderPluginManagerTrait requires array access to read from plugin definitions. This breaks if the definitions are not arrays, or if they are arrays, but use different keys.

Proposed resolution

Ensure plugin definitions are typed using \Drupal\plugin\PluginType\PluginTypeInterface::ensureTypedPluginDefinition() prior to getting the operations provider class name.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.