Restore/repair S3 image uploading in tinymce

[Tathanen]

Description of changes

To get the S3 image uploading in HTML text entry working again:

• Added back the uploadimage tinymce plugin
  • plugin.min.js copied from @kraenhansen's work in NationalMuseumofDenmark/collections-online@85c7c28, along with language files
  • plugin.min.js has been customized to work with Keystone. q("csrf-token") has been replaced with Keystone.csrf.header['x-csrf-token'] in order to successfully grab the csrf token
• Properly required/defined some library code needed for S3FileType.js to function
  • I know this is a deprecated type but it's foundational in this functionality continuing to work. This is just a quick fix for now, a more thorough rearchitecting in the future is probably appropriate.

Related issues

keystonejs/keystone#4388, keystonejs/keystone#3529

Testing

There are like 54 failing tests and none of them have anything to do with this, but just including that per the form.

[Tathanen]

Of note: this is similar to the work done in keystonejs/keystone#4531, but also includes the necessary edits to make the S3 image uploading work, not just cloudinary.

[davidmckenzie]

Really hoping this could be merged soon - it's a blocking issue for me and I'd rather not deviate from master in production :)

@Noviny any chance we could get this merged?

[stennie]

Related: PR #4616 (add tinymce uploadimage plugin)

[stennie]

Thanks for the PR @Tathanen and apologies for the delay in feedback. With some effort we have tests passing in master once again and can start reviewing PRs more sanely.

This appears ok to merge, however I've created a related issue to update to the latest TinyMCE (#4699) which may introduce conflicts. If you're interested in helping with that, any assistance/advice would be appreciated.

Thanks,
Stennie