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

Closes gh-8891

Closes gh-8687

* pr/9055:
  Remove deprecated spring.rabbitmq.listener.* properties
  Polish "Support direct AMQP container"
  Support direct AMQP container

See gh-9055, gh-9108

Closes gh-9055

Add support for auto configuration - select container type and separate
discrete properties.

See gh-9055

Move `spring.rabbitmq.listener.*` to `spring.rabbitmq.listener.simple.*`
in preparation for Spring AMQP 2.0 that supports different container
types.

Closes gh-9108
See gh-9055