Improve TestBuilderResult.

[davidmorgan]

Improvements that help with syncing into google3.

Return build errors, it's very common to check them and you currently have to use a log interceptor to do that.

Return success boolean outputs from BuildResult because it's not a public type, deprecate using it directly. Fix #4100

Give a way to set verbose logging.

[github-actions]

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[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:build	4.0.1	already published at pub.dev
package:build_config	1.2.0	already published at pub.dev
package:build_daemon	4.0.5-wip	WIP (no publish necessary)
package:build_modules	5.0.18	already published at pub.dev
package:build_runner	2.9.1-wip	WIP (no publish necessary)
package:build_test	3.5.0	ready to publish	build_test-v3.5.0
package:build_web_compilers	4.2.4	already published at pub.dev
package:scratch_space	1.1.1	already published at pub.dev

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