feat(process_reports): default --preset to reset-contradictory

This allows terser invocations for invocations without reports
specified, which we've just barely started allowing.

moz-webgpu-cts/src/main.rs

@@ -85,7 +85,7 @@ enum Subcommand {
  #[clap(long = "glob", value_name = "REPORT_GLOB")]
  report_globs: Vec<String>,
  /// The heuristic for resolving differences between current metadata and processed reports.
- #[clap(long)]
+ #[clap(long, default_value = "reset-contradictory")]
  preset: ReportProcessingPreset,
  },
  /// Parse test metadata and re-emit it in normalized form.