contribute a prompt benchmarking script

[devoncarew]

• contribute a prompt benchmarking script

This contributes a contribute a prompt benchmarking script; it gets label information for ~100 existing issues - assumed to be correctly labelled - and compares them against the labels predicted by the prompt. This will allow us to benchmark prompt changes to know whether we're improving things or not. Note that there are no prompt improvements in this PR (just some updates for area label changes).

The benchmarking can be re-run via dart tool/bench.dart.

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[github-actions]

PR Health

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Package	Change	Current Version	New Version	Needed Version	Looking good?

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// Copyright (c) 2024, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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Package publish validation ✔️

Package	Version	Status
package:dart_flutter_team_lints	3.2.0	already published at pub.dev
package:firehose	0.9.2	already published at pub.dev

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