Rudder

The computation of ComplianceLevel is realy inefficient, as it goes on creating many object.

original code was in https://github.com/Normation/rudder/pull/2648/files and is extracted for readability

Test perfs with original method shows:
Computes take ~2000µs first, then ~450µs after 100 iteration, total test is 97038 µs

New compute is ~1000µs for first iteration, ~300µs after 100 iteration, total test is 38208 µs

Old sum is 85µs -> 8µs, total cost 3083µs
New sum is 74µs -> 3µs, total cost 2069µs

JIT does wonder, but still it cannot eradicate all overhead