feat: Add required affinity option to locales resolver

[ericfjosne]

We are hitting an issue with the current setup, where the default behavior for the ICU LocaleMatcher promotes locales which are too distant from what we consider as an acceptable best match.

Examples:

• Norwegian Bokmål nb is promoted as best matching locale for Danish da.
• Indonesian id gets promoted as best matching locale for Malay ms.
• Russian ru gets promoted as best matching locale for Kazakh kk and Mongolian mn.

We would like to enable some level of control over the matching logic. We suggest adding a new requiredLocaleAffinity configuration option, which builds on the locale affinity logic implemented previously.

In order to not break existing integrations, we need to set a default value for this new configuration option. We decided to set it to MUTUALLY_INTELLIGIBLE define over here.