Fix ExtensionContext on instance creation

[JojOatXGME]

Overview

Resolve #1568.
Resolve #2970.
Resolve #3445.

This PR moves the instance creation into the execution context of the test method. This affects the following callbacks:

• TestInstancePreConstructCallback
• TestInstanceFactory
• ParameterResolver (when resolving parameters for the constructor)
• TestInstancePostProcessor

Assuming the test is using TestInstance.Lifecycle.PER_METHOD (the default), these callbacks will now receive the ExtensionContext for the currently executed test method. This has the following effects:

• The callbacks can now access ExtensionContext.getTestMethod()
• ExtensionContext.getTestClass() and TestInstanceFactoryContext.getTestClass() are no-longer interchangeable
• ExtensionContext.getTestClass() now returns the (nested) class of the currently executed test
• Instances of CloseableResource which are added to the store will now be closed at the end of the test execution

If the test is using TestInstance.Lifecycle.PER_CLASS, the behavior is unaltered.

Not sure if the change is considered API breaking. The previous behavior was rather unintuitive and not explicitly documented. However, the example at TestInfoDemo is no-longer valid and has been changed as part of the PR. I also think there is a good chance that there are a few extensions in the wild which rely on the previous behavior, since the behavior was in place for multiple years. I would therefore like to know how I should proceed with the PR.

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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