Add custom provider in official rclone repo

[MircoT]

• Avoid the patch system and add officially the INFN Cloud provider with s3 + sts
• Using oidc-agent as a token retrieving command

[MircoT]

Monitor this pull request:

• https://github.com/rclone/rclone/pull/5757/files

Once it is accepted, try to make a pull request with the AWS SDK 2 that supports the new token retriever interface:

• https://github.com/aws/aws-sdk-go-v2/blob/cc93d47779759286d4b82c0be987afcb5bb0f1e7/credentials/stscreds/web_identity_provider.go#L74

Target -> Include a new provider in the rclone s3 providers chain to get the token via a command (e.g. oidc-token)

Issue to monitor for the support of AWS SDK v2: rclone/rclone#4989