[infra] Try using dart sdk dev release lowerbound

[dcharkes]

Let's try the new workflow where we put the Dart SDK lower bound with the first version that supports the required syntax in both Dart and Flutter (#93).

Let's try to release this, and roll it into Dart and Flutter to see if the new workflow works.

This PR removes all the builders against stable now that we have a dependency on a Dart SDK dev release.

Breaking JSON change in this PR: Start emitting new asset types (namespaced per package). This is not compatible with older versions of the protocol.

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
native_assets_builder	Breaking	0.14.0	0.15.0-wip	0.15.0	✔️
native_assets_cli	Non-Breaking	0.14.0	0.15.0-0	0.14.1	✔️
native_toolchain_c	Non-Breaking	0.11.0	0.12.0-wip	0.11.1	✔️

Changelog Entry ✔️

Package	Changed Files

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

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 symbols

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.

Files
no missing headers

All source files should start with a license header.

Unrelated files missing license headers

Files
pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 77.013%. first build
when pulling 95a8118 on asset-id-namespacing
into 42dd764 on main.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:ffi	2.1.4	already published at pub.dev
package:ffigen	18.1.0	already published at pub.dev
package:jni	0.14.1	already published at pub.dev
package:jnigen	0.14.2-wip	WIP (no publish necessary)
package:native_assets_builder	0.15.0-wip	WIP (no publish necessary)
package:native_assets_cli	0.15.0-0	ready to publish	native_assets_cli-v0.15.0-0
package:native_toolchain_c	0.12.0-wip	WIP (no publish necessary)
package:objective_c	7.1.0	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.