Fix compatibility with package:logger

[natebosch]

Fixes #3514

Add a forwarding implementation of onLevelChanged which was added in
the Logger class.

Update upper bound SDK constraint to avoid pub publish warning.

Remove dependency_overrides section in pubspec.yaml since there is a
separate overrides file.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:build_runner_core	7.2.9	ready to publish	build_runner_core-v7.2.9
package:build_web_compilers	4.0.4-wip	version 4.0.4-wip is pre-release; no publish necessary
package:build_runner	2.4.4	already published at pub.dev
package:build	2.4.1-wip	version 2.4.1-wip is pre-release; no publish necessary
package:scratch_space	1.0.2	already published at pub.dev
package:build_modules	5.0.3-wip	version 5.0.3-wip is pre-release; no publish necessary
package:build_daemon	4.0.1-dev	version 4.0.1-dev is pre-release; no publish necessary
package:build_test	2.2.0-wip	version 2.2.0-wip is pre-release; no publish necessary
package:build_resolvers	2.2.1-wip	version 2.2.1-wip is pre-release; no publish necessary
package:build_config	1.1.2-dev	version 1.1.2-dev is pre-release; no publish necessary

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

[kevmoo]