Add a simple `BootstrapRegistry` that can be used to store and share
object instances across `EnvironmentPostProcessors`. The registry
can be injected into the constructor of any `EnvironmentPostProcessor`.
Registrations can also perform additional actions when the
`ApplicationContext` has been prepared. For example, they could register
the the bootstrap instances as beans so that they become available to
the application.
See gh-22956
2260657781