Add torchgeo pretrained backbones/FMs

[paolofraccaro]

Is your feature request related to a problem? Please describe.
We need to add more FMs to our registry.

Describe the solution you'd like
Given @CarlosGomes98 encoder_decoder refactoring we can easily wrap the models from torchgeo and add them to the registry.

Describe alternatives you've considered (optional)
NA

Additional context (optional)
This links also to the GEO-Bench V2 project, which will use terratorch as the main tool for delivery.

[romeokienzler]

tackle once #186 is merged by @Joao-L-S-Almeida

@paolofraccaro working on this one

[romeokienzler]

@paolofraccaro @Joao-L-S-Almeida trying to merge and re-fork...