Translation Manager: configureClient across core and connectors, Umbraco 19 prep

Core: backoffice client moved to configureClient
Core: Umbraco 19 work. Block and picker changes handled, API client regenerated, Jumoo.Json bumped to 19.0.0-beta1, and custom conditions always answer
Connectors: AI, CSV, DeepL, CrowdIn, SmartCat, LanguageWire, Xliff and TranslatePlus now authenticate with configureClient, with the API secured where it wasn't. Merged forward to v18
GlobalLink: replaced the hand-written client with a generated one, and released 17.1.3 and 18.0.2