Generate translation files from bundles instead of native sources

[Tug]

Fixes #2615
This is an alternative to #2617

This PR contains a change in wp-cli.phar, that is being reviewed here wp-cli/i18n-command#228
It allows makepot to correctly parse our bundled JS and extract translation strings.

Using bundle as the source of truth for strings will make our i18n process less fragile, as any code that is included in it will be used to determine the strings to be translated. In return, we lose the position of those strings in our code as well as translators comments, something that has already been done on gutenberg to automate translations.

TODO:

• Investigate wrong encoding for emoji https://github.com/wordpress-mobile/gutenberg-mobile/pull/2622/files#diff-fadcda321726c553aff8098335f23ab6R101
• Investigate fixing translators comments by creating a dev build that preserve comments

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes more info and have added them to RELEASE-NOTES.txt if necessary.

[mchowning]

I like this approach better than what I have suggested in #2617. Assuming we get the translations and encoding issues you mention resolved, this feels like a much more robust approach to take going forward. Nice work @Tug ! 👍

[mchowning]

Our translations pipeline has undergone a lot of changes (some inspired by this PR), so I'm going to close this.