Revisit complex type merge logic

[philwebb]

In #4313 we changed the way that complex types are merged but this has an impact on the legitimate use-case described in spring-cloud/spring-cloud-config#466.

We need to rethink things again.

[marcellodesales]

@philwebb thanks for looking into this...

[marcellodesales]

Here's another bug that I opened a while ago... When complex types are used, all values MUST have encryption or else it fails.

spring-cloud/spring-cloud-config#452

[philwebb]

I don't think there's a way for us to fix this without introducing regressions. I've reopened the Spring Cloud issue to see if we can fix it there.

[marcellodesales]

@philwebb thanks for looking into this... I will keep an eye on spring-cloud/spring-cloud-config#466