Closes gh-26216

This commit updates websocket and messaging configurations in order
to not use CGLIB proxies anymore. The goal here is to allow support
in native executables and to increase the consistency across the
portfolio.

Closes gh-26227

Closes gh-26226

Closes gh-26225

Closes gh-26030

Closes gh-26211
Co-authored-by: Nfengyuanwei <fengyuanwei@wondersgroup.com>

Closes gh-25490

Closes gh-26166

Closes gh-25927

The previous implementation uses ArrayList for storing resolved
resources and ArrayList has O(n) time complexity for the contains
operation. By switching to the HashSet for storing resolved
resources we improve the time complexity of this operation to be O(1).

See gh-25927

This commit improves the Javadoc for the `ForwardedHeaderFilter`
(Servlet Filter) and `ForwardedHeaderTransformer` (reactive variant) so
as to mention security considerations linked to Forwarded HTTP headers.

Closes gh-26081

Prior to this commit, the `SimpleApplicationEventMulticaster` would be
instrumented with the `ApplicationStartup` and start/stop events for
invoking event listeners (`spring.event.invoke-listener`).

This feature was already limited to single-threaded event publishers,
but is still flawed since several types of events can happen
concurrently. Due to the single-threaded nature of the startup sequence,
our implementation should not produce startup events concurrently.

This can cause issues like gh-26057, where concurrent events lead to
inconcistencies when tracking parent/child relationships.

This commit removes the `spring.event.invoke-listener` startup event as
a result.

Fixes gh-26057

* gh-26133:
  Expose future response in new AsyncServerResponse

This commit introduces AsyncServerResponse, an extension of
ServerResponse that is returned from ServerResponse.async and that
allows users to get the future response by calling the block method.
This is particularly useful for testing purposes.

See gh-25907

This commit adds support for sending Server-Sent Events in WebMvc.fn,
through the ServerResponse.sse method that takes a SseBuilder DSL.
It also includes reference documentation.

Closes gh-25920

Closes gh-26197

Closes gh-26183

Closes gh-26182

Closes gh-26189

Remove the overriden pathVariable method from the nested request
wrapper,so that the merged attributes are used instead of the ones
provided by servlet.

Closes gh-26163

See gh-26170

Closes gh-26170

See gh-26176

Closes gh-26167

The change to copyHeaders from d46091 also applied to copyHeadersIfPresent.

Closes gh-26155

1. Revert changes in setHeader from 5.2.9 that caused regression on self-copy.
2. Update copyHeaders to ensure it still gets a copy of native headers.
3. Exit if source and target are the same instance, as an optimization.

Closes gh-26155

This commit introduces the following changes:
 - Converters/codecs are now used based on generic type info.
 - On WebMvc and WebFlux, kotlinx.serialization is enabled along
   to Jackson because it only serializes Kotlin @Serializable classes
   which is not enough for error or actuator endpoints in Boot as
   described on spring-projects/spring-boot#24238.

TODO: leverage Kotlin/kotlinx.serialization#1164 when fixed.

Closes gh-26147

Closes gh-26151

Closes gh-26134

Applies a change that was intended in #23915 but wasn't.

Closes gh-26119