Update `ConfigDataEnvironment` so that it adds the initial `Binder`
to the `BootstrapContext` for `Bootstrappers` to use.

Closes gh-23401

Refine `OriginTrackedPropertiesLoader` document split detection to be
more lenient if there is trailing whitespace.

Closes gh-23399

* gh-23391:
  Upgrade Java 15 CI image to use the Java 15 GA build

Closes gh-23391

See gh-23391

Closes gh-23397

Closes gh-23396

Closes gh-23395

Closes gh-23394

Closes gh-23393

See gh-23326

Attempt to fix `ConcurrentModificationException` which occurs on
Java 11+.

See gh-23326

Refactor `BootstrapRegistry` support following initial prototype work
with the Spring Cloud team.

This update splits the `BootstrapRegistry` API into `BootstrapRegistry`,
`BootstrapContext` and  `ConfigurableBootstrapContext` interfaces and
moves it to the same package as `SpringApplication`.

A new `Bootstrapper` interface has been introduced that can be added
to the `SpringApplication` to customize the `BootstrapRegistry` before
it's used.

Closes gh-23326

Move `IncompatibleConfigurationFailureAnalyzer` to fix a package tangle.

Closes gh-23385

Relocate `DefaultPropertiesPropertySource` to fix a package tangle.

Closes gh-23383

Closes gh-23379

Closes gh-23188

Closes gh-23187

Closes gh-23388

Closes gh-23186