Fix support for JVM shutdown hooks

[marcphilipp]

Overview

When the ConsoleLauncher is executed via its main method while
passing arguments via its -cp option, it no longer closes the custom
class loader it creates eagerly after test discovery or execution.
Instead, it relies on the JVM shutdown to free up any resource held by
the class loader which is initiated by calling System.exit directly
afterward.

Fixes #4469.

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Definition of Done

• There are no TODOs left in the code
• Method preconditions are checked and documented in the method's Javadoc
• Coding conventions (e.g. for logging) have been followed
• Change is covered by automated tests including corner cases, errors, and exception handling
• Public API has Javadoc and @API annotations
• Change is documented in the User Guide and Release Notes

[sormuras]

Could CustomClassLoaderCloseStrategy.CLOSE_AFTER_CALLING_LAUNCHER be the default? This would keep the amount of changes in existing tests lower. Only the real main path with the terminating System.exit(result) call would use CustomClassLoaderCloseStrategy.KEEP_OPEN.