[web] Fix bug with usage of os.rename under windows environment In 7c386161ebd6 we removed cache handling from property sheet and introduced usage of a tempfile + os.rename to get atomic generation of files. The pb is that this is not portable, since under windows os.rename will raise an exception if the file already exists (because there is no way to write a file atomatically in such case). This kind of thing should be out of the CW scope anyway, so implements a quick & dirty fix in the mean time. Closes #14214794

[migration] More resilient migration script Query the information schema to retrieve existing constraint (primary key and unique) and drop them. Thus don't use anymore DROP CONSTRAINT IF EXISTS (not implemented by e.g. old versions of sqlserver). To do so a missing DISTINCT was necessary to avoid duplicates.