ref: better prioritize and highlight common remote options

[jorgeorpinel]

Extracted from https://peckofpickledpojos.wordpress.com/2020/08/09/learning-dvc-by-trial-and-error
(also related to https://discuss.dvc.org/t/dvc-push-to-public-s3-bucket/457):

ran into the issue of setting up a remote add to my S3 bucket... seemed like a simple credentials issue... It’s a little difficult to find but if you click around to check the remote add command...

DVC-based solution:

$ dvc remote modify myremote credentialpath ~/.aws/credentials

Probably many other remote config options that are only listed in collapsed sections of https://dvc.org/doc/command-reference/remote/modify (already buried inside the > remote cmd ref. nav element). Maybe we should use them more in and link to them more from other examples related to remotes (of which we may need more too), and/or write guides similar to https://dvc.org/doc/user-guide/setup-google-drive-remote for the most common remotes.

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This issue can probably be addressed by several PRs, one per remote type (at least the most commonly used ones: S3, GCS, Azure, SSH)

[jorgeorpinel]

Another example: mention GOOGLE_APPLICATION_CREDENTIALS in https://dvc.org/doc/user-guide/setup-google-drive-remote

From https://discord.com/channels/485586884165107732/563406153334128681/743977450912088134

[jorgeorpinel]

#2866 should cover this.