[android] EphemeralKeyProvider called 4 times

Hi @triniwiz @NathanWalker

Sorry for reporting 3 separated issues but I discover then as i go!

I've seen 4 call to get the Ephemeral key! the problem come from com.stripe.android.CustomerSession.initCustomerSession that accept a 3rd attribute to avoid sending other request when PaymentSession is initialized. see here

We can expose an attribute at the constructor as below but strangely enough setting shouldPrefetchCustomer to false this does prevent the prefetech call but doesn't resolve the problem !! I'll investigate that more, I yhink the problem come from the PaymentSession !

Also Application.android.contextis deprecated for Utils.android.getApplicationContext()

export class StripeStandardCustomerSession {
    constructor(shouldPrefetchEphemeralKey: boolean = false) {
        StripeStandardConfig.shared.initPaymentConfiguration();
        com.stripe.android.CustomerSession.initCustomerSession(StripeStandardCustomerSession.context, createKeyProvider(), shouldPrefetchEphemeralKey);
        this.native = com.stripe.android.CustomerSession.getInstance();
    }
    static get context() {
        return Utils.android.getApplicationContext();
    }
}

Start by reading StripeStandardCustomerSession and the calls to CustomerSession.initCustomerSession, PaymentSession, and createKeyProvider described in the issue. Reproduce or trace the four EphemeralKeyProvider calls, then verify the constructor option and Utils.android.getApplicationContext() behavior; done means the redundant requests and deprecated context usage are resolved.