Node nevermined service refactor

[r-marques]

The node nevermined service https://github.com/nevermined-io/node/blob/main/src/shared/nevermined/nvm.service.ts currently handles to much responsibilities (ipfs, filecoin, s3, ...).

This makes it difficult to work with and modify. This is a problem since this service is handling the different integrations that nevermined has with different 3rd party services.

The goal of this epic is to follow the nestjs best practices and separate all this functionality into different services. Ideally we should have a different service for each integration, and we should use nestjs provided tools instead of more external npm packages:

• Service to handle files stored on S3: upload and download
• Service to handle files stored on ipfs: upload and download
• Service to handle files stored on filecoin: upload and download
• Service to handle files meant to be retrieved by url: download
• Make use of nestjs httpmodule to make http requests https://docs.nestjs.com/techniques/http-module
• Add tests for the services. Specially test failure conditions like 404 when the file does not exist and 401 when there are authorization issues when accessing 3rd party services