Deprecate and remove all legacy common functionality that has already been replaced in the new system

[camilaibs]

Context

Ref: #24493

To prepare for the stable backend release, we will deprecate the backend-common package.

Description

Make sure that all factories, handlers, loaders, routers and other utilities that where mapped to the new system gets deprecated in the backend common package.

Here is a list of things to deprecate:

Note

Since this list was created while reviewing the common API reports for the backend, make sure you revisit it when working on this task.

Alpha api-report:

• Context

Index api-report:

• getRootLogger
• getVoidLogger
• createRootLogger
• createServiceBuilder
• loadBackendConfig
• errorHandler
• requestLoggingHandler
• HostDiscovery

[camilaibs]

Pull request deprecating the logger helpers: #24804

[camilaibs]

Pull request deprecating the service builder: #24814

[camilaibs]

Pull request deprecating the router handlers and context: #24833