Reflectometry: Script Checker

As a POLREF scientist I would like to have a utility in genie_python that helps me check any given script for validity, similar to the `dry_run` flag in reflectometry scripts, i.e. it just prints out what the script would do but not actually do it. There should be a clear distinction from a user interaction point of view between running the script and checking the script. This has cost them time before as they ran a script overnight but forgot to disable dry run.

### Acceptance Criteria
- There is a utility in genie_python that lets you "dry run" any script file, i.e.
1. User types something like `check_script("some_file.py")`,
2. Script is run but any commands contained therein are simply printed to console, nothing is actually set, no runs started etc.

### Notes
We have a genie [simulation mode](https://github.com/ISISComputingGroup/ibex_user_manual/wiki/Simulating-Scripts), it may be enough to have a wrapper that loads a given script and executes any code inside within a `with g.sim.Simulate():` block.