Add support for meta-config to `@HelidonTest`

## Environment Details
* Helidon Version: 2.x
* Helidon SE or Helidon MP 
* JDK version:
* OS:
* Docker version (if applicable):

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## Problem Description
From a Slack conversation, it would be nice if our test extension supported meta-config. (suggested by @tomas-langer)


