Make distinction between Testcontainers for integration tests and development more clear in documentation

[scottfrederick]

The documentation has a section on using Testcontainers for testing. Sub-sections have information specific to integration testing and development-time testing, but this distinction is not clear from the headings. It might be better to separate these two testing concerns into separate sections to make the differences more clear.

[hantsy]

Quarkus Dev and Micronaut test-resources, the background testcontainers are working seamless in those cases running the application and running integration tests.

I really do not understand the purpose of Spring Boot newly introduced test Application class, and some config(such as declaring test containers as beans) are only for the development time.

[eddumelendez]

some config(such as declaring test containers as beans) are only for the development time.

It was fixed in spring boot 3.1.3. See #36661

So, the experience is consistent between testing and development mode