Allow all extensions to access method-level extension context

[marcphilipp]

Overview

The JUnit Jupiter extension API is missing a crucial piece of functionality that comes up and is re-discussed every few weeks/months: there is no way to access the method-level extension context for TestInstancePostProcessor (and other) extensions. This is important to create and destroy resources on the test class instance level. Resolving this issue will reduce friction for users and free up time for maintainers to work on other duties.

Deliverables/tasks

• Introduce EnableTestScopedConstructorContext annotation for extensions #4032
• Decide on name for new annotation/method in team call
• Replace opt-in annotation with extension method #4062 to make it more discoverable and to avoid introducing a new paradigm for changing extension behavior
• Introduce configuration parameter for default extension context scope #4064 to allow testing for compatibility with the new behavior without having to change existing code, in particular wrt. third-party extensions
• Add constructor injection support for TempDir #4060
• Use new extension context scope in core extensions #4065
• Add tests for extension context scope supplied to InvocationInterceptor #4068
• Polish documentation for test-scoped extension context opt-in #4070