Input tracker WIP

[davidmorgan]

For #3811, review and land #3953 first.

WIP: input tracking and serialization to get performance improvements.

[github-actions]

PR Health

Changelog Entry ❗

Package	Changed Files
package:build	build/lib/src/internal.dart build/lib/src/library_cycle_graph/asset_set.dart build/lib/src/library_cycle_graph/asset_set.g.dart build/lib/src/library_cycle_graph/library_cycle.dart build/lib/src/library_cycle_graph/library_cycle.g.dart build/lib/src/library_cycle_graph/library_cycle_graph.dart build/lib/src/library_cycle_graph/library_cycle_graph.g.dart build/lib/src/library_cycle_graph/library_cycle_graph_loader.dart
package:build_resolvers	build_resolvers/lib/src/analysis_driver_model.dart build_resolvers/lib/src/build_asset_uri_resolver.dart
package:build_runner	build_runner/lib/src/server/asset_graph_handler.dart
package:build_runner_core	build_runner_core/lib/src/asset_graph/graph.dart build_runner_core/lib/src/asset_graph/identity_serializer.dart build_runner_core/lib/src/asset_graph/node.dart build_runner_core/lib/src/asset_graph/node.g.dart build_runner_core/lib/src/asset_graph/serialization.dart build_runner_core/lib/src/generate/build.dart build_runner_core/lib/src/generate/input_tracker.dart
package:build_test	build_test/lib/src/in_memory_reader_writer.dart

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