Skip user limit validation when saving cloud licenses

What does this MR do?

Related to #324090

As discussed in #324090, it was decided that the user limit validations on License should be avoided for Cloud Licenses. This will help to streamline the activation process, allowing the customer to activate a subscription (essentially saving the license to their instance) even if the subscription is for less than the purchased quantity. The overage will be reconciled at the first quarterly reconciliation. Beyond that, we will routinely be saving new licenses during cloud sync and these should be saved even if there is an overage.

This MR:

• Skips the check_users_limit validation in the License model if cloud? is true.
• Introduces the License#cloud? method to easily return a boolean for whether the license is a cloud license.

Does this MR meet the acceptance criteria?

Conformity

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