[WIP] Cost-aware Resynthesis

[Nozidoali]

• Set ps.wps.preserve_depth to toggle costfn_resyn
• Choose the resyn solution based on customized cost function
• Support best-cost solution up to 3-resub, and run recursion if >3 resub
• Support cost vector containing size-cost and depth-cost.
• Support XAG resynthesis and AIG resynthesis

[Nozidoali]

xag_resyn test failed

[Nozidoali]

• fix the early return bug in xag_resyn
• implement "slack view" on top of fanout view (foreach_fanout method),
• add test cases of "slack view"
• add test cases of "costfn resub"

[codecov-commenter]

Codecov Report

Merging #518 (52792a0) into master (a3be48d) will increase coverage by 0.20%. The diff coverage is 96.07%.

@@            Coverage Diff             @@
##           master     #518      +/-   ##
==========================================
+ Coverage   82.61%   82.82%   +0.20%     
==========================================
  Files         146      148       +2     
  Lines       18099    18386     +287     
==========================================
+ Hits        14953    15228     +275     
- Misses       3146     3158      +12     

Impacted Files	Coverage Δ
.../mockturtle/algorithms/resyn_engines/xag_resyn.hpp	95.26% <ø> (ø)
...e/algorithms/experimental/boolean_optimization.hpp	62.26% <60.00%> (ø)
include/mockturtle/views/slack_view.hpp	96.42% <96.42%> (ø)
...rtle/algorithms/resyn_engines/xag_costfn_resyn.hpp	96.76% <96.76%> (ø)
...nclude/mockturtle/algorithms/dsd_decomposition.hpp	87.32% <0.00%> (-4.23%)	:arrow_down:
include/mockturtle/views/fanout_view.hpp	98.80% <0.00%> (+0.02%)	:arrow_up:
include/mockturtle/utils/index_list.hpp	93.59% <0.00%> (+0.20%)	:arrow_up:

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[Nozidoali]

• Seperate xag_costfn_resyn from xag_resyn.
• Allow increase area for depth optimization
• Allow tracing solution cost in recursion.