Clean up/organize the docs/codebase

[aqche]

This PR cleans up/organizes the docs/codebase just so it is slightly easier to navigate. List of things this PR does:

• Re-organizes providers into the same categories/order as the one on the Terraform docs in the README.md as well as in cmd/root.go. (I left GCP first 😉)
• Alphabetizes all available resources in the README.md as well as in each _Provider struct's GetSupportedService and GetResourceConnections functions.
• There was a portion of docs describing AWS global resources under the Use with Azure section of the README.md so I moved it to the AWS section.
• Add missing download link for New Relic provider in README.md.
• Cleans up some imports throughout the code.
• Cleans up indentation, capitalization, spacing, punctuation throughout the docs/code.

• Also this PR fixes a small bug in cmd/root.go where newClouflareProvider was missing from the providerGenerators.