HPCC-12564 New regressionsuite option to generate multiple variants

- add code to handle multiple "//version <n1>=<v1>,<n2>=<v2>,..." tag in ECL file
- add code to generates stub(s) for ECl file if //version used conjuction with with //dynamic:source
- add code to make archive from generated stub
- change report code to mark //version tagged file with current parameters in output list
- update README.rst
- add a combined //dynamic and //version tag test to suite

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>