* GH-3679: Better caching for SpringIntegrationTest
Fixes https://github.com/spring-projects/spring-integration/issues/3679
The `@SpringIntegrationTest` makes a test cache key based on its attributes values
when the same application context can be used in different test classes
with different endpoints to have stopped originally.
* Rework an `IntegrationEndpointsInitializer` to the `SpringIntegrationTestExecutionListener`
which consult a `MockIntegrationContext` for endpoints to be started or not before
the test execution and definitely stopped after the test execution to have a flexibility
with the cached context
* Improve a `MockIntegrationContext` to gather `AbstractEndpoint` beans and have them
marked for stopping in the beginning of the application context.
The `SpringIntegrationTestExecutionListener` takes care about startup in its `beforeTestClass()`
* Verify different state for the `SpringIntegrationTest` with the `CachedSpringIntegrationTestAnnotationTests`
* * Improve `SpringIntegrationTestExecutionListener` performance
when no `@SpringIntegrationTest.noAutoStartup()` is configured
* Fix `CachedSpringIntegrationTestAnnotationTests` check `isRunning()`
for the endpoint under the testing instead of `isAutoStartup()`
which is changed in one test class, but not other, and the order
of their execution would matter
* Migrate `MockMessageSourceTests` to JUnit 5 as a roadmap of the whole project
* Fixes https://github.com/spring-projects/spring-integration/issues/3787
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