simplify workflow/dataflow to get wind directions from SLC

[agrouaze]

currently:

1) SLC ->XSARSLC xtiling-> L1B -> tiles corners 2) SLC ->sigma0 calibrated+tiles corners (L1B) -> XSARSLC interface-> patches 3) patches->L2A predictions->wdir

it could be more direct (all in L2A processor):

1) SLC->xsarslc dependance->sigma0+tiles-> in memory patches->L2A predictions->wdir

what would be needed?

• [ ] integrate interface.py in L2A wind dir processor
• [ ] add xsarslc as optional dependency
• [ ] skip production of patches
• [ ] change the code to use L1B datatree in memory instead of the files