Overhaul externalized config data processing

[philwebb]

This is a placeholder issue to group the various tasks required to replace the existing ConfigFileApplicationListener class:

• Add @Name support for value object binding (Add @Name support for value object binding #22492)
• Filter empty YAML documents (Filter empty YAML documents #22493)
• Add ConfigurationPropertySource.from factory method (Add ConfigurationPropertySource.from factory method #22494)
• Add multi-document properties file support (Add multi-document properties file support #22495)
• • Open issue with STS (Add support for Spring Boot multi-document properties files sts4#533)
• • Open issue with IntelliJ (https://youtrack.jetbrains.com/issue/IDEA-250542)
• Add DeferredLogFactory support (Add DeferredLogFactory support #22496)
• Extract DefaultPropertiesPropertySource class (Extract DefaultPropertiesPropertySource class #22520)
• Add CloudPlatform.isEnfoced that uses a Binder (Add CloudPlatform.isEnforced that uses a Binder #22498)
• Replace ConfigFileApplicationListener and rework application properties support (Replace ConfigFileApplicationListener and rework application properties support #22497)
• • Extract EnvironmentPostProcessor
• • Extract RandomValuePropertySourceEnvironmentPostProcessor
• • Add new ConfigData APIs
• • Fail if spring.config.activate.on-profile is specified in a profile specific property file
• • Add additional-meta-data JSON
• Update "external configuration" documentation (Overhaul "externalized configuration" documentation #22521)
• Support profile groups (Add support for profile groups #22522)
• Add volume mount property source support (Add support for creating property sources from volume-mounted Kubernetes ConfigMaps and Secrets #19990)
• Check theme: config-data and theme: profiles issues to see if they can be closed
• Raise issue to consider trimming volume mounted values (Add auto-trimming support to configtree property sources #23826)

[dreis2211]

Isn't Filter empty YAML documents already done in YamlPropertySourceLoader.java#L51 ?

[philwebb]

Isn't Filter empty YAML documents already done

Mostly, but there's a bug if you have a multi-document file since the OriginTrackedYamlLoader wraps types and an empty string isn't treated as empty. I've got a fix prepared to push.