conduit: Pass data dir to plugin config.

[winder]

Summary

Pass a data directory to plugins so that path arguments can be optional.

Test Plan

New unit tests.

[codecov]

Codecov Report

Merging #1357 (b43b0da) into develop (7d7f31e) will decrease coverage by 0.06%.
The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           develop    #1357      +/-   ##
===========================================
- Coverage    62.78%   62.71%   -0.07%     
===========================================
  Files           76       77       +1     
  Lines        10377    10374       -3     
===========================================
- Hits          6515     6506       -9     
- Misses        3303     3308       +5     
- Partials       559      560       +1     

Impacted Files	Coverage Δ
...ugins/processors/blockprocessor/block_processor.go	67.21% <0.00%> (+0.82%)	⬆️
conduit/plugins/processors/noop/noop_processor.go	57.89% <0.00%> (ø)
...ins/processors/filterprocessor/filter_processor.go	80.55% <40.00%> (-2.12%)	⬇️
conduit/plugins/exporters/noop/noop_exporter.go	77.27% <66.66%> (ø)
conduit/pipeline/pipeline.go	64.63% <69.23%> (-1.04%)	⬇️
conduit/plugins/config.go	100.00% <100.00%> (ø)
...duit/plugins/exporters/example/example_exporter.go	88.88% <100.00%> (ø)
...duit/plugins/exporters/filewriter/file_exporter.go	75.47% <100.00%> (-7.87%)	⬇️
...lugins/exporters/postgresql/postgresql_exporter.go	80.23% <100.00%> (ø)
conduit/plugins/importers/algod/algod_importer.go	77.01% <100.00%> (-1.02%)	⬇️
... and 5 more

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[mciccarello]

Looks good to me. I don't see anything that directly conflicts with what I've done with the plugin config strings. However be aware I've changed how they are indented slightly to make it work with conduit init, and I am dependent on that particular format (which I'm not super happy about, but will take time to generalize)