Document bean override support in the TestContext framework in the reference manual

[sbrannen]

Overview

Initial documentation for bean override support in the Spring TestContext Framework (TCF) was introduced in e1bbdf0; however, that documentation resides in the appendix for the testing chapter.

The goal of this issue is therefore to introduce a dedicated subsection (in the TCF section) which documents the "Bean Override" support as a first-class feature. That section should cross-reference the @TestBean, @MockitoBean, and @MockitoSpyBean sections in the appendix.

Related Issues

• Provide a safe way to override and mock beans in the TestContext framework #29917