Clarify supported targets for annotations in the TestContext framework

[sbrannen]

The discussion in #32771 made it apparent that developers can be confused by the generic wording in the Javadoc for annotations in the Spring TestContext Framework (TCF), regarding where developers are allowed to declare such annotations.

For example, the Javadoc for many of the class-level annotations in the TCF states something similar to the following.

@XYZ is a class-level annotation that is used to configure XYZ for an ApplicationContext for integration tests.

Although the statement is true, it does not make it clear that such an annotation is only honored when declared on a test class.

We should therefore make that clear for all effected annotations.