babel-plugin-replace-textdomain: Replace missing domains too

[anomiex]

Changes proposed in this Pull Request:

It should also fix up calls with no domain parameter at all, like
__('foo').

Also, clean up the code a bit, and actually replace the nodes instead of
munging the value (which I'm not sure is actually supported).

Jetpack product discussion

PT: p9dueE-3MG-p2

Does this pull request change what data or activity we track or use?

No

Testing instructions:

• Is CI happy?

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello anomiex! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer and confirm D71391-code works as expected before merging this PR. Once this PR is merged, please commit the changes to WP.com. Thank you!
This revision will be updated with each commit to this PR

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[kraftbj]

I'd rather us not have code in our repo that lacks a textdomain, but that's not a blocker for this.

[anomiex]

We could always have linter rules or the like that require this to be fixed in our own code. But I figured this was quicker than chasing after a missing domain in a Calypso package. Looking at their other code now, they seem to have a mix of not using domains at all and passing __i18n_text_domain__, so we might at some point need to have this plugin start replacing that too.

[github-actions]

Great news! One last step: head over to your WordPress.com diff, D71391-code, and commit it.
Once you've done so, come back to this PR and add a comment with your changeset ID.

Thank you!

[anomiex]

r236554-wpcom