Honor @Primary for UserDetailsService and UserDetailsPasswordService in InitializeUserDetailsBeanManagerConfigurer

[siva-sai-udaygiri]

Motivation

In scenarios where multiple UserDetailsService or UserDetailsPasswordService beans
are defined, Spring may raise NoUniqueBeanDefinitionException or select the wrong
bean without explicit resolution.

Changes

• Added @Primary to UserDetailsService and UserDetailsPasswordService beans in
  InitializeUserDetailsBeanManagerConfigurer
• Ensures deterministic bean selection

Issue Reference

Fixes gh-17902

Testing

• Added a test in InitializeUserDetailsBeanManagerConfigurerTests to validate
  resolution when multiple candidates are present
• Verified that all existing tests pass with ./gradlew check

Notes

• No breaking changes
• Consistent with Spring idioms for bean resolution