Expose moa-based expression evaluation API

Expose moa-based expression evaluation API

This change set introduces a new moa-based expression evaluation API. The currently exposed expression API is left untouched for now, but might be removed in the future in favor of this one.

It's optimized to be used for Input interpolation in the context of a job.

In a future iteration this may be generalized to provide the context key (e.g. job.inputs, or just job) to the evaluator in addition to the inputs - in case it should be used to evaluate inputs in different contexts than just jobs.

This change set also introduces moa as a dependency pinned by SHA. I'd argue that this is enough for now and we can decide on a version strategy for moa at a later point in time. We are expecting lots of changes to moa anyways, so no point in spending time on versioning.

Refs Introduce moa-based expansion API into step-runner (#295)