Since Spring Framework 4.3.0.RC2, a default embedded value resolver
has been registered with the bean factory when one is not otherwise
configured. This meant that placeholders in `@Value` would be resolved
with or without PropertyPlaceholderAutoConfiguration defining a
PropertySourcesPlaceholderConfigurer bean. However, placeholders in
bean definitions would only be resolved if a
PropertySourcesPlaceholderConfigurer was defined.

This commit updates PropertyPlaceholderAutoConfigurationTests to align
with this change in Framework. We now test that placeholders are
resolved in `@Value` annotations with or without the auto-configuration
and that placeholders in bean definitions are only resolved with the
auto-configured.

Closes gh-22230