Support XML properties in ResourcePropertySource

JDK 5 introduced an XML-based properties file syntax. This commit
ensures that when such files are supplied as the underlying resource
for a ResourcePropertySource instance, they are routed appropriately
to Properties#loadFromXML as opposed to Properties#load.

Issue: SPR-9896
Merge branch 'SPR-9896' into 3.2.x

* SPR-9896:
  Support XML properties in ResourcePropertySource
Remove additional xsd versions from reference docs

A few versioned xsd references still existed in xsd-configuration.xml;
this commit removes them, completing the work for SPR-10010

Issue: SPR-10010
Make UriComponents Serializable

Issue: SPR-10186
Fix typo in reference docs

Issue: SPR-10204
MockHttpServletRequest's getParameter(Values) returns null for null parameter name

Issue: SPR-10192
MockHttpServletResponse's getHeaderNames declares Collection instead of Set for Servlet 3.0 compatibility

Issue: SPR-9885
SpringValidationAdapter properly detects invalid value for JSR-303 field-level bean constraints

Issue: SPR-9332
EntityManagerFactoryUtils finds default EntityManagerFactory in parent contexts as well

Also introduces consistent use of getBean(Class) for similar use cases across the framework, accepting a locally unique target bean even if further matching beans would be available in parent contexts (in contrast to BeanFactoryUtils.beanOfType's behavior).

Issue: SPR-10160
Introduced NoUniqueBeanDefinitionException as a dedicated subclass of NoSuchBeanDefinitionException

Issue: SPR-10194
Final preparations for 3.2.1
Support sub-types of ResponseEntity

Issue: SPR-10207
Aligned XML scheduled-task elements with @Scheduled in terms of kicking in after context refresh

Issue: SPR-9231
Introduced NoUniqueBeanDefinitionException as a dedicated subclass of NoSuchBeanDefinitionException

Issue: SPR-10194