Add historical data to l3

[BaptisteVandecrux]

This PR builds on top of #251. It:

• reads merged (raw+tx for v2+v3 stations) aws-l2 data
• runs toL3 on that L2 file
• loads and postprocesses the historical GC-Net data
• appends the historical GC-Net data before the freshly generated L3 data
• makes hourly, daily, monthly resampling and fills metdata

[PennyHow]

I just merged a branch resolving the Github actions issues into here. Now the installation and test processes should work fine.