HPCC-12015 Move the regression suite text files

Move 'download' directory

Update path generation in Test Engine

Test with ./ecl-test setup -t all, result: ok.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
You could add <separator> "download" onto the os version of the path to make them consistent.
Really the variable should be regressionSuiteHppcDownloadDir with the extra ::download, or named as it is without the current ::download.