Make proto3_json.dart aware of well known types

[osa1]

This syncs cl/629836458.

From the CL:

This removes the requirement for proto3_json.dart to invoke outside code
(either via BuilderInfo or inheritance). This also improves tree shaking
of the proto3json helpers, since the proto3json callbacks attached to
BuilderInfo no longer retain those helpers.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:protobuf	5.0.0	(error) pubspec version (5.0.0) and changelog (5.0.0-wip) don't agree
package:protoc_plugin	23.0.0	ready to publish	protoc_plugin-v23.0.0

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

[devoncarew]

lgtm as already reviewed (This syncs cl/629836458).

However, we may consider rev'ing package:protobuf from 4.2.0-wip to 4.2.0 as a separate PR and publishing. That would capture the ~2 changes that are in head but not yet published.

[devoncarew]

Suggested change

	version: 5.0.0
	version: 5.0.0-wip

[osa1]

If I add -wip that breaks dependency resolution in protoc_plugin because it needs to use 5.0.0 and apparently 5.0.0-wip is not considered 5.0.0.

[devoncarew]

Ah! Then not critical as we can choose to ignore the publishing validation failure. You could try a constraint of ^5.0.0-0 to allow pub get to continue - any -foo version will satisfy that - but we'd need to remember to switch to a regular stable constraint before an actual publish. No strong opinions here.