See gh-25733
See gh-25736

We are passing custom values to the constructor of PooledByteBufAllocator in
tests in order to turn of caching. This is based on:
https://github.com/netty/netty/issues/5275#issuecomment-220547057

Netty 4.1.52 has significant changes in PooledByteBufAllocator:
https://github.com/netty/netty/pull/10267

After the changes, our current value for maxOrder=2, which results in
chunkSize=16K, causes an assert failure in PoolChunk where the runSize
exceeds the chunkSize.

See gh-21188

Closes gh-21188
Co-authored-by: NSebastien Deleuze <sdeleuze@vmware.com>

Closes gh-25770

# Conflicts:
#	build.gradle
#	src/docs/asciidoc/core/core-aop-api.adoc

Closes gh-25769

Closes gh-25755

Closes gh-25729
Closes gh-25728

Closes gh-25767

We don't expect a browser to save error responses to a file but we
extend this protection anyway since "inline" is only a suggestion
that shouldn't have any side effects.

Closes gh-25762

This commit makes sure that exceptions emitted by WebClient are wrapped
by WebClientExceptions:

- Exceptions emitted by the ClientHttpConnector are wrapped in a new
  WebClientRequestException.

- Exceptions emitted after a response is received are wrapped in a
  WebClientResponseException

Closes gh-23842

Closes gh-25730

Closes gh-25527

See gh-25174

Closes gh-25753

Closes gh-25485

Closes gh-25671

This is done:
 - For consistency with other Spring projects
 - Because it is probably a better option to use reference instead of
   spring-framework-reference (spring-framework is already present in
   the URL)
 - To improve PDF documentation discoverability

As a consequence:
 - spring-framework-reference HTML documentation is now published
   under reference/html
 - spring-framework-reference/pdf PDF documentation is now published
   under reference/pdf

The following permanent redirect should be created before Spring
Framework 5.3.0 release:
 - current/spring-framework-reference/pdf/* to current/reference/pdf/*
 - current/spring-framework-reference/* to current/reference/html/*

Closes gh-25071

Closes gh-25759

See reactor/reactor-core#2374
All usages of this API are in tests, which are not checking overflow or
concurrent emissions - so a simple replacement with `try***` equivalents
is fine.

See gh-25578

This also switches to the adoptopenjdk-produced binaries for better
consistency with other JDK versions in our CI.