XAG resynthesis engine (re-implementation of ABC's k-resub)

[lee30sonia]

This PR provides a mockturtle-native re-implementation of the k-resub engine in ABC (called xag_resyn_engine in parallel to mig_resyn_engine). Completeness with respect to abcresub is verified. When applied in sim_resub, runtime is usually dominated by SAT-solving (even with pre-stored CEXs), and the overall runtime is similar to ABC.
Also,

• circuit_validator::gate is replaced by index_list for more efficient interfacing.
• mig_resyn_engines.hpp and xag_resyn_engines.hpp are put together in the path algorithms/resyn_engines, and the public interface for all these engines are unified.
• Interfaces of ResubFn in simulation_based_resub_engine are modified.
• sim_aig_resub (enumeration-based resub functor for sim_resub) is removed.

Missing features that will be implemented in future PRs:

• Support of XOR gates.
• The ported abcresub library can be removed from mockturtle.

[coveralls]

Pull Request Test Coverage Report for Build 618381831

• 333 of 388 (85.82%) changed or added relevant lines in 5 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.3%) to 80.054%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
include/mockturtle/algorithms/circuit_validator.hpp	24	25	96.0%
include/mockturtle/algorithms/sim_resub.hpp	28	53	52.83%
include/mockturtle/algorithms/resyn_engines/xag_resyn_engines.hpp	231	260	88.85%

Files with Coverage Reduction	New Missed Lines	%
include/mockturtle/algorithms/sim_resub.hpp	3	54.81%

Totals
Change from base Build 600495590:	0.3%
Covered Lines:	10668
Relevant Lines:	13326

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💛 - Coveralls