Windowing

[hriener]

This PR implements a new windowing procedure.

Brief summary of changes:

• window_view can now be created from three parameters inputs, outputs, and inner nodes. The view does not override foreach_fanout anymore and does not perform the actual computation for determining outputs and inner nodes.
• window_utils provides methods to construct a window: create_window_impl , collect_nodes, collect_inputs, collect_outputs, expand0_towards_tfi, expand_towards_tfi, expand_towards_tfo, levelized_expand_towards_tfo.
• color_view and out_of_place_color_view can be used to manage traversal IDs (the views implement several new API methods: new_color, current_color, clear_colors, color, paint, eval_color, eval_fanins_color).

[coveralls]

Pull Request Test Coverage Report for Build 315096811

• 382 of 398 (95.98%) changed or added relevant lines in 4 files are covered.
• 38 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+0.7%) to 80.163%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
include/mockturtle/views/color_view.hpp	55	57	96.49%
include/mockturtle/utils/window_utils.hpp	275	289	95.16%

Files with Coverage Reduction	New Missed Lines	%
include/mockturtle/algorithms/node_resynthesis/xag_minmc2.hpp	1	92.11%
include/mockturtle/algorithms/dsd_decomposition.hpp	3	87.5%
include/mockturtle/algorithms/mig_resub.hpp	15	21.99%
include/mockturtle/algorithms/resubstitution.hpp	19	80.89%

Totals
Change from base Build 276301805:	0.7%
Covered Lines:	10135
Relevant Lines:	12643

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💛 - Coveralls