[hooks_runner] Add TimelineEvents

[dcharkes]

This PR adds timeline events to the hooks_runner package:

• All FileSystem calls. (With a TracingFileSystem.)
• All Process runs.
• The main methods.

This enables looking at the performance:

(First build compiles the hook and runs the hook. Second build doesn't compile the hook and doesn't run the hook. Side note: Compiling Dart takes longer than running the hook (compiling C)!)

Some quirks:

• The current approach only works for non-concurrent events. (The stdout and stderr file logging is concurrent to the process calls and therefore has to be excluded.) If we ever start doing things concurrently, we'll need to refactor this.
• There are a lot of possibilities to improve things when we have more than one hook in the system. Optimizing this only makes sense once we have more real world projects using hooks.
• Tracking issues for improving the performance: [native_assets_builder] Compile and run hooks in parallel #1288 [native_assets_builder] The asset builder system should compile hook/{build,link}.dart once. #1578

The one improvement made in this PR is that we stop hashing the kernel file contents. Saving a hook invocation if the kernel file didn't change (~300ms) if the hook sources only had a whitespace change seems less valuable than saving the hashing of the hook kernel file on every invocation (~50ms). After this change, cached hook invocations take ~30ms per hook on the local test cases.

Closes: #2236

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:code_assets	0.19.3	already published at pub.dev
package:data_assets	0.19.1	(error) pubspec version (0.19.1) and changelog (0.19.2) don't agree
package:ffi	2.1.4	already published at pub.dev
package:ffigen	19.0.0	already published at pub.dev
package:hooks	0.19.3	already published at pub.dev
package:hooks_runner	0.20.2	ready to publish	hooks_runner-v0.20.2
package:jni	0.14.2	already published at pub.dev
package:jnigen	0.14.2	already published at pub.dev
package:native_doc_dartifier	0.0.1-pre	already published at pub.dev
package:native_toolchain_c	0.16.2	already published at pub.dev
package:objective_c	8.0.0	already published at pub.dev
package:swift2objc	0.0.1-wip	WIP (no publish necessary)
package:swiftgen	0.0.1-wip	WIP (no publish necessary)

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[github-actions]

PR Health

Changelog Entry ✔️

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Changes to files need to be accounted for in their respective changelogs.

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The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

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License Headers ✔️

// Copyright (c) 2025, 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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no missing headers

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Unrelated files missing license headers

Files
pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/native_doc_dartifier/example/native_doc_dartifier_example.dart
pkgs/native_doc_dartifier/lib/native_doc_dartifier.dart
pkgs/native_doc_dartifier/lib/src/native_doc_dartifier_base.dart
pkgs/native_doc_dartifier/test/native_doc_dartifier_test.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 85.305% (+0.02%) from 85.285%
when pulling 261a66a on developer-timeline
into ad157d1 on main.

[goderbauer]

Does this actually work? I was under the impression that code in asserts has to be synchronous? A quick experiment in dartpad with assert(await Future.value(false)); also seems to indicate that it wouldn't fire as expected...

[goderbauer]

Actually, never mind. This works. Dartpad doesn't have asserts enabled it seems.

[goderbauer]

nit: Include a note that this used _fileSystemUntraced under the hood.

[goderbauer]

LGTM