[code_assets] Support custom target OS and Architecture

[dcharkes]

Closes: #3411

Closes: #1258

Enables

extension OhosOS on OS {
  static final ohos = OS.fromString('ohos');
}

to work properly.

The other open enums in the JSON schema that were not open in the Dart API:

• architecture
• sanitizer

Link mode and link mode preference should be closed:

• [code_assets] Make LinkMode and LinkModePreference closed #3462

If we were to add code assets already presigned and prepackaged in xcodeframeworks for example, it would be a new asset type, rather than new option for the existing asset type.

Because we don't have a pub workspace for FFIgen and JNIgen with the other packages, we now need many more pubspec overrides. Basically before it was kinda working without a complete set of overrides because the inconsistent set of deps (half from the repo, half from pub) managed to resolve. This is no longer true with pushing code_assets to v2.0.0.

[github-actions]

PR Health

Breaking changes ⚠️

Package	Change	Current Version	New Version	Needed Version	Looking good?
hooks	Non-Breaking	2.0.2	2.1.0-wip	2.1.0-wip	✔️
code_assets	Non-Breaking	1.2.1	2.0.0-wip	2.0.0-wip	✔️
hooks_runner	Non-Breaking	1.5.0	1.6.0-wip	1.6.0-wip	✔️
native_toolchain_c	Non-Breaking	0.19.2	0.19.3-wip	0.19.3-wip	✔️
objective_c	Non-Breaking	9.4.1	9.4.2	9.5.0 Got "9.4.2" expected >= "9.5.0" (non-breaking changes)	⚠️

This check can be disabled by tagging the PR with skip-breaking-check.

API leaks ✔️

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.

Package	Leaked API symbol	Leaking sources

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[github-actions]

Package publishing

If you have publishing permissions, you can use the links below to publish the changes after merging this PR.

Package	Version	Status	Publish tag (post-merge)
package:code_assets	2.0.0	ready to publish	code_assets-v2.0.0
package:data_assets	0.20.0	already published at pub.dev
package:ffi	2.2.0	already published at pub.dev
package:hooks	2.0.2	already published at pub.dev
package:hooks_runner	1.6.0-wip	WIP (no publish necessary)
package:jni_flutter	1.0.1	already published at pub.dev
package:jni_util	1.0.0-wip	WIP (no publish necessary)
package:native_toolchain_c	0.19.3-wip	WIP (no publish necessary)
package:record_use	0.6.1-wip	WIP (no publish necessary)
package:swift2objc	0.2.0	already published at pub.dev
package:swiftgen	0.1.3-wip	WIP (no publish necessary)

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

[dcharkes]

@goderbauer I'm not entirely sure what to do with link mode preference and link mode:

• Extensibility of link mode is somewhat problematic, because it's likely more than a string. And it's not namespaced with a package. So different third_parties (or us) might not agree on what fields the link mode should have.
• Introducing new link modes is also problematic, because we don't communicate in the protocol which link modes are supported yes or no. So a packages' link hook doesn't know if they emit something in a specific link mode.
• And introducing link mode preferences will not work either.

If we decide to lock it down, then the way to add something later from our side would be to make a new asset type package:code_assets/code_asset_v2. And have new link modes there.

And I can't think of a link mode we would add in the first place.

WDYT about locking it down instead of making it extensible?

[goderbauer]

WDYT about locking it down instead of making it extensible?

Yeah, given that it is highly questionable that we'll ever add another mode (famous last words): Let's lock it down.

[dcharkes]

Unrelated CI failures:

• [objective_c] CI build-flutter-example failing #3445
• [objective_c] Xcode version not available on CI? #3463
• [jnigen][infra] Flaky NoClassDefFoundError #838

[dcharkes]

WDYT about locking it down instead of making it extensible?

Yeah, given that it is highly questionable that we'll ever add another mode (famous last words): Let's lock it down.

Made a separate PR for this:

• [code_assets] Make LinkMode and LinkModePreference closed #3462

[goderbauer]

LGTM