Feature: add native getDeviceData method

[audrius-sav]

There was no way to get device data from BrainTree without calling native payment flow methods like showPaypalModule() or tokenizeCard(). Device data should be sent to your server when user has already vaulted his PayPal account (https://developer.paypal.com/braintree/docs/guides/paypal/vault/android/v4#collecting-device-data).
Changes:

• Added native getDeviceData methods to only call Data Collector and resolve promise with the result.

[audrius-sav]

@vasylnahuliak
Some changes, pls review when you can 🙏
Слава Україні! 🇺🇦

[vasylnahuliak]

Taken for testing

[vasylnahuliak]

It works.
Thanks!

[vasylnahuliak]

🎉 Released in v2.3.0 https://github.com/ekreative/react-native-braintree/releases/tag/v2.3.0

[paskalov-aris]

To-Do:

• Android. Check if we can split the logic in the getDeviceData method to call new DataCollector(mBraintreeClient).collectDeviceData() only once (it seems like it's currently may be called a second time from the setup method)
• iOS. Try to use the new getDeviceData method in other methods, such as tokenizeCard, showPayPalModule

[vasylnahuliak]

@aris-paskalov Thanks! Added into README https://github.com/ekreative/react-native-braintree/tree/master#todo