Add the function to delete OpenStack Snapshot in the SPA

@masami @yas

Regarding getEntity() in OpenStackOperationsService and AwsCloudOperationsService,
it is implemented to use EntityDeleteFormTrait trait.
Which of the following should be written?

// Plan A: Does not describe the return type
  public function getEntity() {
    return $this->entity;
  }

// Plan B: Describe only EntityInterface type
  public function getEntity(): EntityInterface {
    return $this->entity;
  }

// Plan C: Adapt to form notation
  public function getEntity(): ContentEntityInterface|RevisionLogInterface {
    return $this->entity;
  }

@ryo-yamashita

According to the comment at https://git.drupalcode.org/project/drupal/-/blob/9.5.x/core/lib/Drupal/C..., it looks Plan B.

Thanks

@masami

Can you please take a look at the comments? Thanks

@masami @yas

I have read the patch and it looks good. Thanks.

@ryo-yamashita

Thank you for your review.

@masami

Thank you for the update. I'll merge the patch to 4.x and 5.x, and close this issue as Fixed.