[MAJOR] Fixed support for passing params and options to retrieve methods

[prathmesh-stripe]

Changelog

• Singleton retrieve method now requires params to be passed as the first argument. Existing calls to singleton retrieve method with only opts argument will have to be updated to account for the addition of params argument.

params = { expand: ["available"] }
opts = { stripe_account: "acct_123" }

# ❌ No longer works
Stripe::Balance.retrieve(opts)

# ✅ Correct way to call retrieve method
Stripe::Balance.retrieve(params, opts)

[helenye-stripe]

Should the merge-base of this be our next-major branch?