Workflow improvement: Support new EIA data format in build_hydro

[euronion]

The EIA data format from our datasource changed. Suggestions

• Automatic download of EIA data OR update the EIA .csv file with hydro generation to new dataformat
• substitute the vresutils dependency in build_hydro by writing the pd.read_csv statement directl.y

Originally posted by @euronion in https://github.com/PyPSA/pypsa-eur/pull/321#issuecomment-1059728440

[fneum]

This was addressed in #342.

Keep open until #347 is in via #342.