Migrate Webdev Repo into SDK

[jyameo]

This initiative is a major migration focused on moving the entire dart-lang/webdev repository containing webdev, dwds, and frontend_server_client into the Dart SDK's workspace. The goal is to eliminate the current separation and fully integrate our essential web development toolchain with the Dart SDK . The primary objective is to centralize maintenance, improve CI consistency by leveraging SDK infrastructure, and reduce friction in SDK-driven workflows.

• go/migrating-webdev

[mit-mit]

@jyameo can you please add a short description in the top-most comment? The go-link is not generally accessible.

[jyameo]

@jyameo can you please add a short description in the top-most comment? The go-link is not generally accessible.

Thanks for the reminder! I've just updated a description of the migration project.