Let users specify the lags the time series pipelines should compute in AutoMLSearch

As a user of EvalML for time series problems, I expect to be able to configure a set of lags all time series pipeline should compute. This would let me incorporate my business knowledge into the search.

Came up during the design of #2733. I think it will be a useful feature but this is nice-to-have for down the road as it's blocked by other issues and it's not part of our beta requirements.