Improve statistics command line flag

[phate]

The statistics command line flags for jlc and jlm-opt are very verbose and partly non-descriptive. The following should be done:

1. Improve the descriptiveness of the statistics command line flags. They should describe/reflect the (optimization) pass they are gathering statistics for.
2. We should transform the statistics flag into a comma separated list: --statistics=statistics1, statistics2,...

[haved]

The duplication I was referencing is the set of statistics options listed both at
https://github.com/phate/jlm/blob/master/jlm%2Ftooling%2FCommandLine.cpp#L512

and

https://github.com/phate/jlm/blob/master/jlm%2Ftooling%2FCommandLine.cpp#L771

Which can be nicely deduplicated by replacing the individual command line flags by a single comma separated string.

Also, the mapping between StatisticsId and statistic name can use a BiMap :)