[Feature]: Support Region enums to simplify setup of Terminal API live endpoints

[gcatanese]

Feature summary

Support Region enums to simplify setup of Terminal API live endpoints

Problem statement

Similarly as implemented in the Java library, the Node Library should provide a better support to define the region-specific live URLs:

Region	Data Center	Sync	Async
Australia	au	https://terminal-api-live-au.adyen.com/sync	https://terminal-api-live-au.adyen.com/async
East Asia	apse	https://terminal-api-live-apse.adyen.com/sync	https://terminal-api-live-apse.adyen.com/async
Europe	eu (*)	https://terminal-api-live.adyen.com/sync	https://terminal-api-live.adyen.com/async
United States	us	https://terminal-api-live-us.adyen.com/sync	https://terminal-api-live-us.adyen.com/async

(*) eu is the default endpoint

Proposed solution

Implement Regions enums and refactor the code that defines the TerminalAPI endpoints

Simplify the creation of Client object to standardise the approach (use Config object)

const config = new Config({
    apiKey: "myApiKey",
    environment: "LIVE",
    liveEndpointUrlPrefix: "myPrefix",
    region: RegionEnum.US
});
client = new Client(config);