[async] Generate DOT graph for StateFlowGraph

[k-ye]

• The initial node is drawn as a box
• The latest state owners are drawn with double edges

Generated DOT graph for misc/visualize_state_flow_graph.py:

digraph {
  n_initial_state_0 [label="[node: initial_state:0]",shape=box]
  n_foo_c4_0_clear_list_0 [label="[node: foo_c4_0_clear_list:0]"]
  n_foo_c4_0_listgen_0 [label="[node: foo_c4_0_listgen:0]"]
  n_foo_c4_0_clear_list_1 [label="[node: foo_c4_0_clear_list:1]"]
  n_foo_c4_0_listgen_1 [label="[node: foo_c4_0_listgen:1]"]
  n_foo_c4_0_struct_for_0 [label="[node: foo_c4_0_struct_for:0]",peripheries=2]
  n_foo_c4_0_clear_list_2 [label="[node: foo_c4_0_clear_list:2]"]
  n_foo_c4_0_listgen_2 [label="[node: foo_c4_0_listgen:2]",peripheries=2]
  n_foo_c4_0_clear_list_3 [label="[node: foo_c4_0_clear_list:3]"]
  n_foo_c4_0_listgen_3 [label="[node: foo_c4_0_listgen:3]",peripheries=2]
  n_bar_c6_0_struct_for_0 [label="[node: bar_c6_0_struct_for:0]",peripheries=2]

  n_initial_state_0 -> n_foo_c4_0_listgen_1 [label="S2dense_mask"]
  n_initial_state_0 -> n_foo_c4_0_listgen_3 [label="S2dense_mask"]
  n_initial_state_0 -> n_foo_c4_0_clear_list_1 [label="S2dense_list"]
  n_initial_state_0 -> n_foo_c4_0_clear_list_0 [label="S1pointer_list"]
  n_initial_state_0 -> n_foo_c4_0_listgen_0 [label="S1pointer_mask"]
  n_initial_state_0 -> n_foo_c4_0_listgen_2 [label="S1pointer_mask"]
  n_initial_state_0 -> n_foo_c4_0_struct_for_0 [label="S3place_i32_value"]
  n_foo_c4_0_struct_for_0 -> n_bar_c6_0_struct_for_0 [label="S4place_i32_value"]
  n_foo_c4_0_listgen_0 -> n_foo_c4_0_clear_list_2 [label="S1pointer_list"]
  n_foo_c4_0_clear_list_2 -> n_foo_c4_0_listgen_2 [label="S1pointer_list"]
  n_foo_c4_0_clear_list_0 -> n_foo_c4_0_listgen_0 [label="S1pointer_list"]
  n_foo_c4_0_clear_list_1 -> n_foo_c4_0_listgen_1 [label="S2dense_list"]
  n_foo_c4_0_listgen_1 -> n_foo_c4_0_struct_for_0 [label="S2dense_list"]
  n_foo_c4_0_listgen_1 -> n_foo_c4_0_clear_list_3 [label="S2dense_list"]
  n_foo_c4_0_clear_list_3 -> n_foo_c4_0_listgen_3 [label="S2dense_list"]
  n_foo_c4_0_listgen_3 -> n_bar_c6_0_struct_for_0 [label="S2dense_list"]
}

Visualization:

I also added a launch_id to SFG's node. IMO this allows us to have a slightly more clear view of the nodes, rather than using pointer as the identifier.

Related issue = #742

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[codecov]

Codecov Report

Merging #1852 into master will decrease coverage by 0.05%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1852      +/-   ##
==========================================
- Coverage   44.16%   44.11%   -0.06%     
==========================================
  Files          44       44              
  Lines        6075     6082       +7     
  Branches     1088     1089       +1     
==========================================
  Hits         2683     2683              
- Misses       3223     3230       +7     
  Partials      169      169              

Impacted Files	Coverage Δ
python/taichi/misc/util.py	18.18% <0.00%> (-0.76%)	⬇️

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[yuanming-hu]

Very cool!! Thank you. The implementation LGTM.