✨ Pre- and Post-Mapping Optimizations

[burgholzer]

This PR adds the facilities to conduct pre- and post-mapping optimizations in QMAP.
At the moment, this merely contains a simple post-mapping optimization that tries to cancel adjacent CNOT gates.

Futhermore, this PR adopts the clone() functionality provided by the QFR library to clone the circuit upon importing it in the respective mapper in order to avoid side effects of the circuit optimizations conducted inside the mapper.

Finally, this PR slightly changes how gate counts for the resulting circuit are reported. Instead of separately listing the number of single-qubit gates, CNOTs, and SWAPs for the resulting circuit, the results now just list the number of resulting single-qubit and CNOT gates. The number of SWAPs, direction reverses, or teleportations directly resulting from the mapping is now listed in the stats part of the mapping result.

[codecov]

Codecov Report

Merging #56 (b9d4898) into main (50c3765) will increase coverage by 0.1%.
The diff coverage is 96.2%.

@@           Coverage Diff           @@
##            main     #56     +/-   ##
=======================================
+ Coverage   89.6%   89.8%   +0.1%     
=======================================
  Files         22      22             
  Lines       1677    1698     +21     
=======================================
+ Hits        1504    1525     +21     
  Misses       173     173             

Impacted Files	Coverage Δ
include/configuration/Configuration.hpp	0.0% <ø> (ø)
src/Mapper.cpp	93.0% <91.8%> (-1.0%)	⬇️
include/Mapper.hpp	58.0% <100.0%> (+6.3%)	⬆️
include/MappingResults.hpp	63.3% <100.0%> (ø)
src/exact/ExactMapper.cpp	97.9% <100.0%> (ø)
src/heuristic/HeuristicMapper.cpp	93.8% <100.0%> (-0.2%)	⬇️

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