Refactor Fastlane email submission state management in Classic Checkout (5095)

[danieldudzic]

This PR is dependent on #3598

Description

This PR will update the email submission state management with a centralized ButtonStateManager.

Steps to test

1. In Classic Checkout, enter a Fastlane profile email address and verify that the OTP dialog appears
2. Try to complete the order, and make sure the transaction fails
3. Return to the checkout page
4. Confirm that the OTP gets triggered for the session pre-filled email address
5. Test against any regressions for other Fastlane transactions in the Classic Checkout

[github-actions]

Test using WordPress Playground

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What's included:

• ✅ WordPress (latest)
• ✅ WooCommerce (latest)
• ✅ PayPal Payments plugin v3.1.0-pr3637-17962368600-g198d3e3 (built from this PR)

Login credentials:

• Username: admin
• Password: password

Plugin Details:

• Version: 3.1.0-pr3637-17962368600-g198d3e3
• Commit: 198d3e3
• Artifact: woocommerce-paypal-payments-3.1.0-pr3637-17962368600-g198d3e3

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