Remove backtraces on error when running rerun binary

[emilk]

What

• Closes Unexpected stack trace when loading a file with no data-loader support. #4738

Starting in anyhow 1.0.77, a backtrace will be printed on error if RUST_BACKTRACE is set, and we set RUST_BACKTRACE=1 in:

rerun/crates/re_log/src/setup.rs

Lines 32 to 35 in d204936

	if std::env::var("RUST_BACKTRACE").is_err() {
	// Make sure we always produce backtraces for the (hopefully rare) cases when we crash!
	std::env::set_var("RUST_BACKTRACE", "1");
	}

We do this because we want to print stack traces on panics.

However, for anyhow::Error our error messages should be good enough to not require a stack trace,
so with this PR we now explicitly print out the error instead of relying in the formatting that happens when returning anyhow::Result from main.

Result

❯ cargo run -p rerun-cli --quiet -- .github/workflows/documentation.yaml    
[2024-01-09T10:09:31Z INFO  re_data_source::load_file] Loading ".github/workflows/documentation.yaml"…
Error: ".github/workflows/documentation.yaml" -> No data-loader support for ".github/workflows/documentation.yaml"

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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[Wumpf]

great find! 👌