[FEATURE] step counter for executor

[nima-siboni]

Feature

Adding step counter to the base system in jax redesign.

Proposal

A new variable is added to the store of the executor.

Testing

Tests are:

• the counter should start from zero.
• at the end of each episode the counter should show increase equal to the number of steps in the episode.
• from one episode to the next episode the counter is not resetted.

Definition of done

• the executor's store has a step counter.
• the tests are passed

Mandatory checklist before making a PR

• [ ] The success criteria laid down in “Definition of done” are met.
• [ ] Code is documented - docstrings for methods and classes, static types for arguments.
• [ ] Code is tested - unit, integration and/or functional tests are added.
• [ ] Documentation is updated - README, CONTRIBUTING, or other documentation.
• [ ] All functional tests are green.
• [ ] Link experiment/benchmarking after implementation (optional).

Links / references / screenshots