HPCC-12022 New //dynamicsource tag

- add code to handle //dynamic:source tag in ECL file
- add '--dynamic source=cluster_list|all' CLI parameter handling
- add code to generates stub for ECl file tagedd with //dynamic:source
- add code to generates multiple instance of //dynamic tagged ECl in suite list
- add code to make archive from generated stub
- change report code to mark //dynamic tagged file with source in output list
- update built-in help and README.rst
- add simple //dynamic tag test to suite

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>