Previously, the infrastructure provided by WebMvcConfigurationSupport
and WebFluxConfigurationSupport can lead to unexpected results due to
the lack of qualifier for certain dependencies. Those configuration
classes refer to very specific beans, yet their injection points do not
define such qualifiers. As a result, if a candidate exists for the
requested type, the context will inject the existing bean and will
ignore a most specific one as such constraint it not defined. This can
be easily reproduced by having a primary Validator whereas a dedicated
"mvcValidator" is expected. Note that a parameter name is in no way a
constraint as the name is only used as a fallback when a single
candidate cannot be determined.

This commit provides explicit @qualifier metadata for such injection
points, renaming the parameter name in the process to clarify that it
isn't relevant for the proper bean to be resolved by the context.

Closes gh-23887