Debug-printing a Report uses `Debug` despite crate docs stating `Display` is used by default

[LunarLambda]

Per https://docs.rs/rootcause/latest/rootcause/handlers/index.html#1-formatting-function-selection :

The default behavior is to always use Display formatting, regardless of how the report itself is being formatted.

All built-in handlers (Error, Display, Debug, Any) use this default behavior, which means they use their display method even when the report is being debug-formatted with {:?}.

However, testing:

// [dependencies]
// rootcause = "0.12.1"

use rootcause::prelude::*;

fn main() -> Result<(), Report> {
    std::fs::File::open("/nonexistent").attach("test")?;

    Ok(())
}

yields (returning Err from main causes Error: {e:?} to be printed):

 ● Os { code: 2, kind: NotFound, message: "No such file or directory" }
 ├ src/main.rs:2
 ╰ "test"

And indeed, digging through the code, Report's Debug impl passes in FormattingFunction::Debug here, which gets threaded to DefaultReportFormatter::format_reports, which asks for the preferred formatting function for Debug here, and then, presumably ought to return a context using FormattingFunction::Display but doesn't, and thus eventually format_item uses Debug.