* Validation script batches only samples
In this change, the validation script will batch only sample generation.
For meta and documentation, it will always be iterative.
Also made changes to meta-codegen*.sh so conditionals which may invoke
maven are explicitly rooted.
* [ci] batch python-experimental, include new springboot option
* [meta] Support Kotlin meta generator
* Guard against automatic scripts (assumptions for this script are not fulfilled by some CI which run "run all" type scripts)