Issue: SPR-17536

ResolvableType-based matching consistently respects generic factory method return type (even for pre-initialized raw singleton instance)

Issue: SPR-17524

(cherry picked from commit ebbe14c3)

Also includes Apache HttpClient 4.5.6 and HttpAsyncClient 4.1.4.

Issue: SPR-17439

Issue: SPR-17492

Issue: SPR-17508

(cherry picked from commit f5aeb814)

Issue: SPR-17518

Issue: SPR-16405
Issue: SPR-15600

Issue: SPR-17476

(cherry picked from commit 362c59c3)

Issue: SPR-17445

(cherry picked from commit ea3250c8)

Issue: SPR-17374

(cherry picked from commit dc1e3b46)

Issue: SPR-17414

Issue: SPR-17413

(cherry picked from commit dd2ce206)

Issue: SPR-17417

(cherry picked from commit 83a54dba)

Issue: SPR-17392

(cherry picked from commit da23505e)

Issue: SPR-17384

(cherry picked from commit 00b7782b)

Prior to this commit, the `ResourceUrlEncodingFilter` would wrap the
response and keep a reference to the request. When
`HttpServletResponse.encodeURL` is later called during view rendering,
the filter looks at the request and extracts context mapping information
in order to resolve resource paths in views.

This approach is flawed, when the filter is used with JSPs - if the
request is forwarded to the container by the `InternalResourceView`,
the request information is overwritten by the container. When the view
is being rendered, the information available in the request is outdated
and does not allow to correctly compute that context mapping
information.

This commit ensures that that information is being extracted from the
request as soon as the `ResourceUrlProvider` is set as a request
attribute.

Issue: SPR-17421
(Cherry-picked from cf25efc7)

The fix for SPR-17178 switched from debug to warn level warning for
all sub-classes of AbstractHandlerExceptionResolver where the request
concerned the DefaultHandlerExceptionResolver only.

This commit restores the original DEBUG level logging that was in
AbstractHandlerExceptionResolver from before SPR-17178. In addition
DefaultHandlerExceptionResolver registers a warnLogCategory by default
which enables warn logging and hence fulfilling the original goal
for SPR-17178.

Issue: SPR-17383

Issue: SPR-17318

Issue: SPR-17286

Issue: SPR-17374

(cherry picked from commit 5f2d47a1)

Issue: SPR-17320

Avoid automatically unwrapping the request in TestDispatcherServlet,
if we find the MockAsyncContext.

Issue: SPR-17353

Issue: SPR-17295

Issue: SPR-17299

(cherry picked from commit 333e3272)

Keep supporting legacy usage of Iterator.remove on getBeanPostProcessors result List in AbstractBeanFactoryBasedTargetSourceCreator and ScriptFactoryPostProcessor (and similarly designed integrations).

Issue: SPR-17286

Declaring beanPostProcessors (and also embeddedValueResolvers) as CopyOnWriteArrayList prevents ConcurrentModificationExceptions in case of concurrent registration/access attempts.

Issue: SPR-17286