chore(payments): upgrade @fluent/bundle to 0.16, @fluent/react to 0.1…

[chenba]

This is @stasm's PR #6098 (which is a follow-up to #6096/#6152) rebased on latest main.

Because

• Fluent packages used to ship two build artifacts: index.js written in the most current ES version, and compat.js transpiled to ES2017. In Remove compat.js build artifacts projectfluent/fluent.js#472 we removed the compat.js builds and set tsc to target ES2018.
• I didn't think it was appropriate for upstream Fluent to make the decision about the browsers supported by the compat.js builds. It's something that app developers should have more control over.
• The expectation is that apps using Fluent will be able to transpile node_modules dependencies to match their browser compatibility requirements.

This pull request

• Is based on chore(payments): upgrade to @fluent/react 0.12.0 #6096. Only the last commit is new compared to chore(payments): upgrade to @fluent/react 0.12.0 #6096
• Upgrades three @fluent packages used by payments-server: @fluent/bundle, @fluent/react, @fluent/langneg to their newest versions which ship ES2018 code.
• As far as I was able to verify it, the files built with yarn build in build/static/js are transpiled by FxA's build system correctly to match your browerlist config.

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).