Previously, Reactor Netty was the only embedded server that enabled
H2C by default. This commit updates the factory to only enable HTTP/2
when SSL has also been configured, aligning it with Jetty, Tomcat,
and Undertow.

If H2C is required, it can be enabled using a NettyServerCustomizer:

@Bean
NettyServerCustomizer h2cCustomizer() {
    return (httpServer) ->
           httpServer.protocol(HttpProtocol.HTTP11, HttpProtocol.H2C);
}

Closes gh-17867

Closes gh-16289

Closes gh-18239

This commit makes sure that any subsequent call on addProtocolResolver
on the context will impact the ResourceLoader implementation that
DevTools sets on the context.

This makes sure that any custom ProtocolResolver that is set later in
the lifecycle is taken into account.

Closes gh-17214

Closes gh-18236

Closes gh-18212

Closes gh-17937

Closes gh-17430

Closes gh-18001

Closes gh-17986

Closes gh-17885

Closes gh-18234

Prior to this change, the custom port configured for the RSocket
server would not be used if the server factory is using the
websocket transport and is provided with a custom
`ReactorResourceFactory`.

Fixes gh-18200

* pr/18214:
  Polish Add Testable to CLASS_ANNOTATIONS in TestTypeExcludeFilter"
  Add Testable to CLASS_ANNOTATIONS in TestTypeExcludeFilter

Closes gh-18214

See gh-18214

See gh-18214

* pr/18151:
  Polish "Add ROLLING_FILE_NAME_PATTERN for File Appender"
  Add ROLLING_FILE_NAME_PATTERN for File Appender

Closes gh-18151

See gh-18151

This new property allows to customize `fileNamePattern` if it is set.
Otherwise, a default pattern remains. Also, new property is supported
`logging.pattern.rolling-file-name`.

See gh-18151

See gh-18232

Closes gh-18227

Closes gh-18205

Closes gh-18226

Closes gh-18225

Previously, the upgrade to Flyway 6 broke compatibility with Flyway
5.2 due to the use of method references that refer to two methods
that do not exist in Flyway 5.2.

This commit replaces the method references with lambdas that are only
called if the user sets the related property. Unless a new-in-Flyway-6
property is set, the auto-configuration will work as before. When such
a property is set the auto-configuration will fail with a
NoSuchMethodError. This approach was chosen to make the
incompatibility clear.

We have also introduced support for passing any JavaMigration beans
in the context into Flyway. This too relies on API that is new in
Flyway 6. It is possible (although unlikely) that users had
JavaMigration beans in Spring Boot 2.1 that were being ignored. This
commit restores this behaviour when using Flyway 5.2.

Closes gh-18193

Closes gh-18222

* pr/18216:
  Fix minor typo

Closes gh-18216

The phrase `We have you covered.` is a sentence and so it should start
with a capital `W`.

See gh-18216

Closes gh-18219

Update `Bindable` builder methods so that existing annotations are
retained.

Closes gh-18218

* pr/18206:
  Polish "Use Duration for ServerProperties.Jetty.idleTimeout"
  Use Duration for ServerProperties.Jetty.idleTimeout

Closes gh-18206

See gh-18206

See gh-18206

* pr/18192:
  Polish

Closes gh-18192

See gh-18192

Closes gh-18209

This commit applies `ServerRSocketFactoryCustomizer` beans to RSocket
setups when the RSocket server is being plugged into an existing Reactor
Netty web server.

Fixes gh-18208