Update CHANGELOGs for release

[osa1]

@sigurdm @devoncarew do you have anything else to add to this release?

Note: pubspec versions are already have the right versions (no -wip suffix).

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:protobuf	5.0.0	ready to publish	protobuf-v5.0.0
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.

[sigurdm]

I'm good

[osa1]

We could release fixnum and bump fixnum dependency here, to get the perf benefits with the new fixnum.

I restarted the g3 job to roll fixnum to g3 in https://dart-review.googlesource.com/c/sdk/+/449020 to see if the issues with conditional imports was fixed.

[sigurdm]

Would the new fixnum not be compatible? Such that we really don't need to change the constraint?

[devoncarew]

do you have anything else to add to this release?

Nope - lgtm!