Refined tests for FactoryBean return type resolution on @Bean methods

Issue: SPR-11842
Polishing
Reference documentation consistently refers to Apache HttpComponents instead of outdated Commons HttpClient

Includes overhaul of remaining references to J2SE and J2EE, consistently replacing them with "the JDK" and "Java EE".

Issue: SPR-11853
Polish assertions and Javadoc for ResourceDatabasePopulator