mvnd and .mvn

I would like the configuration in `.mvn/maven.config` to be used no matter the executable (mvn, mvnw, mvnd).

Currently mvnd (via the new maven wrapper type=only-script) doesn't consider those properties, e.g. `-Dorg.slf4j.simpleLogger.defaultLogLevel=warn`

This is surprising behaviour. There's no mention at https://github.com/apache/maven-mvnd of any files in .mvn/maven.config, jvm.config, extensions.xml so its not clear what the relationship is.

Start by comparing how mvn, mvnw, and mvnd with the type=only-script wrapper handle .mvn/maven.config. Check the related .mvn/jvm.config and extensions.xml behavior and the existing discussion to determine the intended relationship. Done means the configuration behavior is consistent or clearly documented for all named executables.

Written by the indexing model from the issue text.