Before this change the new partial downloads code was causing symlinks
to be copied as regular files.
This was because the partial isn't named .rclonelink so the local
backend saves it as a normal file and renaming it to .rclonelink
doesn't cause it to become a symlink.
This fixes the problem by not copying .rclonelink files using the
partials mechanism but reverting to the previous --inplace behaviour.
This could potentially be fixed better in the future by changing the
local backend Move to change files to and from symlinks depending on
their name. However this was deemed too complicated for a point
release.
This also adds a test in the local backend. This test should ideally
be in operations but it isn't easy to put it there as operations knows
nothing of symlinks.
Fixes#7101
See: https://forum.rclone.org/t/reggression-in-v1-63-0-links-drops-the-rclonelink-extension/39483
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