Update license handling to combine instance/device counts as one

[knolleary]

Part of #3477

Objective: Simplify the license generation process by removing the distinction between Devices and Instances.

New Process: Generate licenses based on the total number of Node-RED Runtimes. This total will include all Hosted Instances and Devices on the platform. Customers will have the flexibility to allocate these runtimes across their devices and hosted instances as they see fit, without any predefined restrictions.

[knolleary]

Our existing license includes claims on the following limits:

• users
• teams
• projects
• devices

The objective here is to collapse projects and devices into a single unified value that represents the combined total. We can take this opportunity to use the name instances to represent this combined total and retired the projects/devices claims. This will also help distinguish between the type of license.

We need to make sure this change does not impact any existing licensed user; if the license contains separate projects/devices claims then we continue to treat them as separate limit. This is going to complicate some of the limit checking as it needs to be aware of both scenarios.

Currently the platform-wide limit checks are scattered around the code base at the point of creation of the associated things. I'm going to pull that into a single place.

We also need to update the reporting of the limits on the api and in the frontend.