Closes gh-23128

Prior to this commit, if a subclass of
org.springframework.web.servlet.view.AbstractView or
org.springframework.web.reactive.result.view.AbstractUrlBasedView
configured a custom value for the requestContextAttribute, that value
was overwritten with null whenever the View was dynamically
instantiated by a UrlBasedViewResolver, and this could lead to
confusing behavior for users of the View.

This commit addresses this issue by ensuring that the
UrlBasedViewResolvers in spring-webmvc and spring-webflux do not
override the requestContextAttribute in a View if the
UrlBasedViewResolver has not been explicitly configured with a custom
requestContextAttribute value.

Closes gh-23129

Closes gh-23133

This commit declares the model method parameter as @Nullable and adds
defensive guards against a null model argument.

Closes gh-23105

Closes gh-22798

See gh-23105

See gh-23105

This commit improves the FreeMarker macro support in spring-webflux by
automatically exposing a RequestContext under the name
"springMacroRequestContext" for use with Spring's FreeMarker macros in
spring.ftl.

This aligns with the user experience for FreeMarkerView in spring-webmvc.

Closes gh-23105

Rationale: @Nullable is not visible in the spring-context-indexer
project.

Closes gh-23117

Closes gh-22981

Prior to this commit, exceptions thrown while closing an InputStream in
AbstractResource were silently ignored.

This commit improves diagnostics for such failure scenarios by logging
the exception at DEBUG level.

Closes gh-23116

Update `FormatterRegistry` with `addPrinter` and `addParser` methods
that can be used to register Printer or Parser implementations in a
similar way to the existing `addFormatter` method.

Closes gh-23110

See gh-23052

Closes gh-23111

Closes gh-23064

Closes gh-23063