rclone: change cache directory to $XDG_CACHE_HOME/rclone

[aguirre-matteo]

Description

Closes #8288.

Checklist

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[teto]

it is safe to backport I guess since it's just a cache ?

[aguirre-matteo]

Yeah, I guess so.

[home-manager-ci]

Successfully created backport PR for release-25.11:

• [Backport release-25.11] rclone: change cache directory to $XDG_CACHE_HOME/rclone #8297