Add settings to support 2 public API keys: one for CA and one for USA

According to documentation each account should have 2 public API keys, one for CA and one for USA. We started working on this here 📌 Add settings to support global payments Fixed but didn't finish it because updating the account to have 2 public API keys is taking too long.
So in the scope of this issue, we need:

1. Separate the single public API key field into "USA public API key" and "Canada public API key" fields.
2. Use the public API key according to the Default locale configuration, which can be altered.