'tar_extract' function fails if there is a linked folder in workingdir that matches one in the tar file

[jgsogo]

Changelog: Bugfix: 'tar_extract' function was failing if there was a linked folder in the working dir that matches one inside the tar file. Now we use the destination_dir as base directory to check this condition.
Docs: omit

closes #4959

[jgsogo]

Not for a minor, it is almost a corner-case, but I would add it to the next release.

[klimkin]

Unlikely, but what if the dest dir has a similar symlink? Will it be safer creating an empty temporary directory?

[jgsogo]

The destination directory could also have the symlink issue, which in turn opens the question of what to do with existing folders and files with the same name as those in the tar file (I'm not sure what Conan is doing in such cases).

With this change, it won't happen with packages (we clean the target directory before extracting) but can still happen with utilities from the tools module that make use of the same code. In those cases, the user is extracting to a local folder that could be not-empty. If we output a warning for these conflicting files (#4966) I think that the user will be able to handle it.

A different approach, as you suggest, would be to extract the zip to a temporary folder and then copy it to the destination dir, but this additional copy could be slow for big packages (or packages with thousands of small files).

[memsharded]

@klimkin @jgsogo Irrespective of the possibility of colliding with a previously existing file, I am merging this now, as it is already an improvement and is fixing a bug that didn't make sense.