Simplify release and changesets-pr workflows

[nedsalk]

Note

Blocked by:

• chore: refactor release workflow #3678

After the merge of #3678, we can do the following to simplify our workflows further:

1. The changeset:update-changelog command can be split into two, one command for updating the changesets PR's changelog and another for updating the GitHub release's changelog. The current command does both based on the PUBLISHED flag, but we don't need this flag anymore as the workflow the command was originally written for has been split.
2. Consider replacing the FuelLabs/changesets-action@main action usage with simple run: | ... step-by-step flows, because both creating/updating the changesets PR and releasing the packages should be straightforward. We don't need this action's dual publish+versioning behavior anymore after chore: refactor release workflow #3678.