[ENH] Introduce AutoSARIMA forecaster

[TonyBagnall]

refactoring of code from #2828

@alexbanwell1 currently ARIMA seems to automatically include seasonal components (SARIMA). I would like to separate these out.

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I have added the following labels to this PR based on the title: [ $\color{#FEF1BE}{\textsf{enhancement}}$ ].
I would have added the following labels to this PR based on the changes made: [ $\color{#31FCCD}{\textsf{forecasting}}$ ], however some package labels are already present.

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[alexbanwell1]

Otherwise looks like the code I wrote, so should be fine!

[TonyBagnall]

will need to revisit this once ARIMA is in