HPCC-10859 Change regress script and update README

Rename regress to ecl-test
Update built-in help texts and README.rst
Fix setup dir related problem, based on the package doesn't contain any
test/setup code.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
HPCC-10859 Change regress script and update README

Rebase to merge changes.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>