feat(filter): Add Country, Currency and Timezone filters

[ndench]

Draft PR to go along with #5835

TODO (if we want to move forward with this feature request):

• Support other comparison types (NEQ, CONTAINS, etc)
• Support multiple choices
• Allow limiting the available countries/timezones/currencies
• Write tests

[javiereguiluz]

@ndench thanks for proposing this feature. I like it and I'll help you with anything you need to complete this.

From the list of things to do, I'd say that:

• Support other comparison types (NEQ, CONTAINS, etc): Nice to have if not very complex
• Support multiple choices: Nice to have if not very complex
• Allow limiting the available countries/timezones/currencies: Let's leave it for the future unless trivial to implement
• Write tests: Not mandatory to merge this, let's do it only if not very complex

Thanks!