Add a script that downloads UCD data for a given Unicode version,
unpacks it, and copies the used files to appropriate locations inside
the Qt source code.
Also update the README and use an HTTPS link for the UCD data file.
FTP links are no longer supported by some browsers.
Task-number: QTBUG-94359
Change-Id: I2aa70a588f675e411fa6b3ce5b4444a7c07ed707
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
