Refactor build state

[davidmorgan]

WIP, land #4165 first.

[github-actions]

PR Health

Changelog Entry ❗

Package	Changed Files
package:build_runner	build_runner/bin/build_runner.dart build_runner/bin/src/commands/clean.dart build_runner/lib/build_runner.dart build_runner/lib/src/build_plan.dart build_runner/lib/src/build_runner.dart build_runner/lib/src/build_runner_command_line.dart build_runner/lib/src/build_script_generate/bootstrap.dart build_runner/lib/src/build_script_generate/build_script_generate.dart build_runner/lib/src/commands/build_command.dart build_runner/lib/src/commands/build_filter.dart build_runner/lib/src/commands/build_options.dart build_runner/lib/src/commands/build_runner_command.dart build_runner/lib/src/commands/clean_command.dart build_runner/lib/src/commands/daemon_command.dart build_runner/lib/src/commands/daemon_options.dart build_runner/lib/src/commands/run_command.dart build_runner/lib/src/commands/run_options.dart build_runner/lib/src/commands/serve_command.dart build_runner/lib/src/commands/serve_options.dart build_runner/lib/src/commands/test_command.dart build_runner/lib/src/commands/test_options.dart build_runner/lib/src/commands/watch_command.dart build_runner/lib/src/daemon/asset_server.dart build_runner/lib/src/daemon/daemon_builder.dart build_runner/lib/src/entrypoint/base_command.dart build_runner/lib/src/entrypoint/build.dart build_runner/lib/src/entrypoint/clean.dart build_runner/lib/src/entrypoint/options.dart build_runner/lib/src/entrypoint/run.dart build_runner/lib/src/entrypoint/run_script.dart build_runner/lib/src/entrypoint/runner.dart build_runner/lib/src/entrypoint/serve.dart build_runner/lib/src/entrypoint/test.dart build_runner/lib/src/entrypoint/watch.dart build_runner/lib/src/generate/build.dart build_runner/lib/src/generate/watch_impl.dart build_runner/lib/src/internal.dart build_runner/lib/src/package_graph/build_config_overrides.dart build_runner/lib/src/server/server.dart build_runner/lib/src/watcher/change_filter.dart build_runner/pubspec.yaml
package:build_runner_core	build_runner_core/lib/build_runner_core.dart build_runner_core/lib/src/asset/finalized_reader.dart build_runner_core/lib/src/asset_graph/graph.dart build_runner_core/lib/src/asset_graph/optional_output_tracker.dart build_runner_core/lib/src/environment/build_environment.dart build_runner_core/lib/src/environment/create_merged_dir.dart build_runner_core/lib/src/generate/build.dart build_runner_core/lib/src/generate/build_definition.dart build_runner_core/lib/src/generate/build_directory.dart build_runner_core/lib/src/generate/build_runner.dart build_runner_core/lib/src/generate/build_series.dart build_runner_core/lib/src/generate/input_matcher.dart build_runner_core/lib/src/generate/options.dart build_runner_core/lib/src/options/testing_overrides.dart build_runner_core/lib/src/package_graph/apply_builders.dart build_runner_core/lib/src/package_graph/target_graph.dart build_runner_core/lib/src/util/build_dirs.dart build_runner_core/lib/src/validation/config_validation.dart
package:build_test	build_test/lib/src/test_builder.dart build_test/pubspec.yaml

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