Handle symbol sets in covoar

Original author: Alex

The covoar tool should be changed to handle all symbol sets for a coverage run rather than being called by coverage.py for each symbol set.

Currently, coverage.py calls covoar once for each symbol set found in the symbol-sets.ini configuration file. This leads to a lot of redundancy. For each symbol set, covoar has to process the objdumps and the coverage information of all the executables even though they do not change.

Changing covoar to process all symbol sets and generate reports in one invocation will result in a large speedup.

This will also require a minor modification to coverage.py to generate the correct .ini file and only call covoar once.