refactor: Remove obsolete SpringFactoriesLoader#loadFactoryNames

[livk-cloud]

• Use ImportCandidates#load instead of SpringFactoriesLoader#loadFactoryNames
• Use EnvironmentPostProcessorsFactory#getEnvironmentPostProcessors instead of SpringFactoriesLoader#loadFactoryNames

There is currently no better way to use SpringFactoriesLoader#loadFactoryNames in org.springframework.cloud.commons.util.SpringFactoryImportSelector#selectImports.
This may not necessarily produce better results, but isn't it a better thing to remove these obsolete methods
I hope the Spring Cloud team will come up with a better opinion.