Accept input and output as typed interfaces in the AI request events

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Problem/Motivation

Now the AI Event constructors accept the $input argument as mixed type in the class Drupal\ai\Event\AiProviderRequestBaseEvent, and the same for $output in the Drupal\ai\Event\AiProviderResponseBaseEvent.

There should be always typed data, as I understand:
- input: Drupal\ai\OperationType\InputInterface
- output: Drupal\ai\OperationType\OutputInterface

Keeping this as mixed requires adding additional checks on each function that works with input and output data, and producing questions on how to process data that doesn't implement those interfaces.

Proposed resolution

Set types for the input and output attributes:
- input: Drupal\ai\OperationType\InputInterface
- output: Drupal\ai\OperationType\OutputInterface

Remaining tasks

Optional: Other details as applicable (e.g., User interface changes, API changes, Data model changes)