Prepare beta release for build_web_compilers

[simolus3]

Having a published pre-release of build_web_compilers with dart2wasm support makes it much easier for package authors to test that everything works before the stable 3.6 release.

If coordinating these releases is too much effort I can also just close this, but I think there's a pretty low risk of breaking anyone since we depend on a pretty recent SDK in build_web_compilers.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:build_web_compilers	4.1.0-beta.0	ready to publish	build_web_compilers-v4.1.0-beta.0
package:build	2.4.2-wip	WIP (no publish necessary)
package:build_config	1.1.2-wip	WIP (no publish necessary)
package:build_daemon	4.0.3-wip	WIP (no publish necessary)
package:build_modules	5.0.10-wip	WIP (no publish necessary)
package:build_resolvers	2.4.3-wip	WIP (no publish necessary)
package:build_runner	2.4.13-wip	WIP (no publish necessary)
package:build_runner_core	7.3.3-wip	WIP (no publish necessary)
package:build_test	2.2.3-wip	WIP (no publish necessary)
package:scratch_space	1.0.3-wip	WIP (no publish necessary)

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

[github-actions]

PR Health

Changelog Entry ✔️

Package	Changed Files

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

Package publish validation ✔️

Package	Version	Status
package:build_web_compilers	4.1.0-beta.0	ready to publish
package:build	2.4.2-wip	WIP (no publish necessary)
package:build_config	1.1.2-wip	WIP (no publish necessary)
package:build_daemon	4.0.3-wip	WIP (no publish necessary)
package:build_modules	5.0.10-wip	WIP (no publish necessary)
package:build_resolvers	2.4.3-wip	WIP (no publish necessary)
package:build_runner	2.4.13-wip	WIP (no publish necessary)
package:build_runner_core	7.3.3-wip	WIP (no publish necessary)
package:build_test	2.2.3-wip	WIP (no publish necessary)
package:scratch_space	1.0.3-wip	WIP (no publish necessary)

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