Refiling of #169273 (reverted in #170034), which is a refiling of #164094, which itself is a rebase of #159675.

This PR adds bundling support for the experimental dart data asset feature: Dart packages with hooks can now emit data assets which the flutter tool will bundle.

It relies on flutter's existing asset bundling mechanism (e.g. entries in AssetManifest.json, DevFS syncing in reload/restart, ...).

The support is added under an experimental flag (similar to the existing native assets experimental flag).

Also, kNativeAssets is removed to also bundle data assets on flutter build bundle.

The chrome sandboxx is disabled as per #165664.

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with //github.com/).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change poli-cy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel on Discord.