Run multiple baselines

Currently you can only run PSRule with one baseline at a time.

There are several scenarios that running multiple baselines in a single execution would be ideal.

When PSRule is loaded there is a small amount of overhead in both PSRule and CI systems that makes multiple runs less performant as compared to a single execution.

Cases for multiple baselines:

1. Using a baseline from two different modules.
2. Using two different baselines in combination i.e. WAF Security and Reliability.
3. Using a required and optional baseline. i.e. This is the minimum mandatory rules that will break the pipeline vs these are the nice to haves that are ideal but won't break the pipeline.

(2) An alternative approach is to use a custom baseline instead.