Hi L2 - Correctly handle when input PSETs don't all contain same esa_energy_steps

[subagonsouth]

Algorithm Description:

Currently, there is a check implemented that ensures all PSETs have the same set of esa_energy_steps. This is because Tim is uncertain if the projection code will correctly handle a missing energy step. My comment in the PR this comes from was:

It is currently a hard requirement because the projection code only bins by spatial pixel. It requires that the variable being projected has the same dimension sizes as the map variable that it projects into. Now that I am writing this, I actually don't know if it is true. I don't know enough about the xarray broadcasting to know what will happen if one of the PSETs is missing an energy step. I know that it can't handle the case where the first PSET is missing an energy step because the map variables are instantiated based on the coordinates of the first PSET.

This ticket is for testing to make sure it works in the mapping code and then modify the Hi code to allow for different energy_steps. This may require pre-loading all PSET energy steps to get the union across all input PSETs.