Introduce AotContextLoader SPI in the TestContext framework

[sbrannen]

Overview

In order to support AOT build-time processing within the Spring TestContext Framework (TCF), we need a way to signal to SmartContextLoader implementations that they should load the test's ApplicationContext without refreshing it or registering a JVM shutdown hook.

In addition, we also need a way for a SmartContextLoader to participate in context loading during AOT run-time execution.

Related Issues

• Add support for processing test contexts ahead-of-time #28204

[sbrannen]

Reopening to introduce a dedicated AotContextLoader extension of SmartContextLoader instead of modifying the existing contract for SmartContextLoader.