feat(wdl-gauntlet): ENTER THE ARENA

[a-frantz]

The goal of THE ARENA is to ensure new lints produce sane warnings for WDL "in the wild".

New --arena flag for wdl-gauntlet that ignores all syntax errors (ParseError or ValidationFailure) and instead just reports LintWarning. This comes with it's own config file, Arena.toml.

Arena has been seeded with 3 repos and their warnings, but that's probably worth revisiting. My process for these 3 was simple elimination starting from Gauntlet.toml. I ran --arena on each of those 13 repos and excluded anything that returned an overwhelming number of Warnings. That was 10 of the 13 😬 .

While testing out arena on some of the test repos I've already logged issues (#50) with existing warnings.

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