Upgrade Guide: Reflect changes in service registration in NServiceBus v10

[danielmarbach]

Relates to the changes introduced in

Particular/NServiceBus#7439
Particular/NServiceBus#7445
Particular/NServiceBus#7428
Particular/NServiceBus#7516
Particular/NServiceBus.CustomChecks#635

This pull request updates the NServiceBus v10 upgrade documentation to clarify how infrastructure components (such as handlers, sagas, behaviors, installers, and custom checks) are registered and resolved. The documentation now emphasizes that these components are no longer registered in the service collection, aligning NServiceBus with modern .NET architectural practices and principles such as the Dependency Inversion Principle and the Hollywood Principle. The changes explain the rationale, impact, required code adjustments, and benefits for users upgrading to v10.

Service registration and architectural changes:

• Infrastructure components (handlers, sagas, behaviors, installers, custom checks) are no longer registered in the service collection, preventing accidental dependency on framework internals and discouraging the Service Locator anti-pattern.
• Documentation explains that dependency injection for handler dependencies continues to work, but direct resolution of handlers/sagas from IServiceProvider is no longer possible.
• Guidance is provided for refactoring code that previously resolved infrastructure types directly, recommending extraction of business logic into proper application services.

Benefits and alignment with .NET practices:

• The change maintains a clean separation between framework and application layers, mirroring established patterns in ASP.NET Core, Blazor, and Minimal APIs.
• Fewer service registrations result in faster validation, fewer false positives