extract: rework the extraction of a package

Before for each file /a/path/to/a/file we were creating a temporary
file: /a/path/to/a/.pkgtemp.file.XXXZZZ (creating the missing directories
if needed).
The problem with this approach is during upgrades, an element of the path
could be changed to become a file and vice versa which would break the
upgrade.

Now we are checking each element of the path until we do find a directory
which exists eg: considering /a/path/to is a file in the old package
/a/path/to/a/file will become /a/path/.pkgtemp.to.XYZ/a/file

at the end of the extraction (after old files have been removed)
all the temporary directories are renamed after their final name.

As a side effect at best we reduce the number of I/O as we reduce the number
of renmaes that are needed