Prefer `utf8mb4_bin` and `utf8mb4_unicode_ci` collations

[carusology]

See this helpful comment from @bgrainger:

One should always use utf8mb4 in order to support non-BMP characters such as Emoji and Chinese.

I believe he's right. We should do this. This will involve downstream changes in our closed source code in Gambit as well in order for these collations to remain consistent.

[carusology]

Need to update QueryTranslator.fs