* pr/9145:
  Improve `HashMapSessionConfiguration`

This commit updates `MapSessionRepository` bean definition return type
and applies equivalent change to `SessionAutoConfigurationTests`.

These changes also ensure compatibility with Spring Session 2.0 which
will merge `ExpiringSession` API with `Session` API.

Closes gh-9145

This commit allows to specify a deprecation level to a manual metadata
entry. The purpose of that new attribute is to distinguish cases where
the property is still bound (default) from cases where the property no
longer exists and won't be bound.

This gives the opportunity to IDEs to still show the property as an
error and offer documentation and an action to rename it if a
replacement exists.

Closes gh-9074

Closes gh-9159

Closes gh-6258

Closes gh-9155

Closes gh-9019

Closes gh-9149

See gh-8714 and 9480e09c

Closes gh-8049

Closes gh-8714

Closes gh-8968

Significantly rework `ConfigurationPropertyName` in an attempt to reduce
the amount of memory and garbage produced. The name elements are now
stored as CharSequences and whenever possible subsequences are used.

This helps to reduce the memory footprint since the underlying char
array can be shared between the source string, and the individual
elements.

For example: `ConfigurationProperty.of("foo.bar.baz")` will return
a name that provides access to the elements `foo`, `bar` and `baz`.
However, these three names all share the same char[], just using
different offsets and lengths.

See gh-9000

Improve ConfigurationPropertySource support by reworking some of the
stream calls based on advice offered by Tagir Valeev from JetBrains.

Also improved ConfigurationPropertySource.containsDescendantOf so that
it returns an enum rather than an Optional<Boolean> (again based on
feedback from Tagir).

See gh-9000

Rework the ConfigurationPropertySources and related adapter classes to
help with performance. The ConfigurationPropertySources class now only
monitors for updates when `.attach` is used. The `.get` methods now
return the adapted version, but no longer checks to see if sources have
been added or removed on each call.

This commit also fixes a few caching issues and makes both the
`PropertyMapper` implementations true static singletons.

See gh-9000

Refactor `ConfigFileApplicationListener` to use a `MultiValueMap` when
loading sources. The helps to simplify the code and removes the need
for the inner `LoadedPropertySources` class. We're also able to delete
the now unused `EnumerableCompositePropertySource` and
`PropertySourcesLoader` classes.

Fixes gh-9144

Closes gh-7461

This reverts commit a8b10f74.

See gh-7461

Closes gh-7461

This commit makes sure the integration tests use the same versions as
the one managed by `spring-boot-dependencies` (including Maven plugins).

Closes gh-8947

* pr/9132:
  Upgrade to Spring AMQP 2.0.0.M4

Closes gh-9132

* pr/9072:
  Add Membrane Spring Boot Starter

Closes gh-9072

Closes gh-9129

* pr/9103:
  Polish

Closes gh-9103

* pr/9116:
  Upgrade to Spring Kafka 1.1.5.RELEASE

Closes gh-9116

Closes gh-9112