feature/improve diff commands

[omissis]

• chore: make GitProtocol attribute on the Downloader struct not exposed as there was no need to have it public
• feat: introduce dependencies cache
• feat: introduce distribution cache
• fix: work around issues caused to cache by tools renamings
• feat: introduce concurrent dependencies downloads
• feat: introduce concurrent tools and modules downloads
• fix: format go code
• fix: remove linting issues
• feat: add unit tests
• chore: rename eks and distribution folders in apis folder to match their provider's names
• chore: refactor internal/eks folder
• chore: refactor diff cluster command
• feat: introduce diff command for the distribution phase, laid out work for the other ones