Add static graph visualization powered by ggraph

[wlandau]

Summary

static_drake_graph() and render_static_drake_graph() now support static graph visualization powered by ggraph. The layout is kind of cramped, but with clusters, this is not so bad.

library(drake)
load_mtcars_example()
config <- drake_config(my_plan)
static_drake_graph(config)

Related GitHub issues

• Ref: Static ggraph visualization #279, Offload all visualization to separate tools #282

Checklist

• I have read drake's code of conduct, and I agree to follow its rules.
• I have read the guidelines for contributing.
• I have listed any substantial changes in the development news.
• I have added testthat unit tests to tests/testthat to confirm that any new features or functionality work correctly.
• I have tested this pull request locally with devtools::check()
• This pull request is ready for review.
• I think this pull request is ready to merge.

[codecov-io]

Codecov Report

Merging #464 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #464   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          66     67    +1     
  Lines        5563   5628   +65     
=====================================
+ Hits         5563   5628   +65

Impacted Files	Coverage Δ
R/drake_graph_info_utils.R	100% <ø> (ø)	⬆️
R/vis_drake_graph.R	100% <100%> (ø)	⬆️
R/static_drake_graph.R	100% <100%> (ø)
R/utils.R	100% <100%> (ø)	⬆️

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