Add get_irradiance_components function #2850

Is your feature request related to a problem? Please describe.
When wanting to test different decomposition models in batch, I find myself having to iterate a decomp_model string list and use a if/else structure which calls the appropriate decomposition model or store the decomposition function into an external variable decomp_func = getattr(pvlib.irradiance, decomp_model).

Describe the solution you'd like
Having a get_irradiance_components, a decomposition equivalent to get_total_irradiance, would do the same trick as the getattr and be built-in within pvlib.

Additional context
get_total_irradiance could likely work as a template for what I'm suggesting.