Use FC Lite as fallback flow in FC SDK

[mats-stripe]

Summary

Motivation

Testing

Changelog

[github-actions]

⚠️ Public API changes detected:

StripePaymentSheet

Public API

-@preconcurrency import WebKit

StripeFinancialConnectionsLite

Public API

+// swift-compiler-version: Apple Swift version 6.3.1 effective-5.10 (swiftlang-6.3.1.1.2 clang-2100.0.123.102)
+// swift-interface-format-version: 1.0
+// swift-module-flags-ignorable: -no-verify-emitted-module-interface -formal-cxx-interoperability-mode=off -interface-compiler-version 6.3.1
+// swift-module-flags: -target arm64-apple-ios15.0-simulator -enable-objc-interop -enable-library-evolution -swift-version 5 -O -enable-experimental-feature DebugDescriptionMacro -enable-bare-slash-regex -module-name StripeFinancialConnectionsLite
+@_exported import StripeFinancialConnectionsLite
+@preconcurrency import WebKit
+import AuthenticationServices
+import Foundation
+import StripeCore
+import Swift
+import UIKit
+import _Concurrency
+import _StringProcessing
+import _SwiftConcurrencyShims

StripeFinancialConnections

Public API

-import CoreMedia
+import StripeFinancialConnectionsLite

If you are adding a new public API consider the following:

• Do these APIs need to be public or can they be protected with @_spi(STP)?
• If these APIs need to be public, assess whether they require an API review.

If you are modifying or removing a public API:

• Does this require a breaking version change?
• Do these changes require API review?

If you confirm these APIs need to be added/updated and have undergone necessary review, add the label modifies public API to this PR to acknowledge the interface change.
Additionally, if you modified or removed an existing API, ensure you update the changelog to reflect the necessary version bump for your changes. Regular public API changes require a MAJOR version bump, and SPI API changes (other than declarations using only @_spi(STP) and/or @_spi(ReactNativeSDK)) require a MINOR or MAJOR version bump.

ℹ️ If this comment appears to be left in error, make sure your branch is up-to-date with master.

[github-actions]

🚨 New dead code detected in this PR:

HostController.swift:104 warning: Assign-only property 'financialConnectionsLite' is assigned, but never used
FinancialConnectionsSessionFetcher.swift:11 warning: Redundant protocol 'FinancialConnectionsSessionFetcher' (never used as an existential type)
FinancialConnectionsSessionFetcher.swift:15 warning: Redundant protocol conformance 'FinancialConnectionsSessionFetcher'
FCLiteAuthFlowViewController.swift:22 warning: Assign-only property 'webAuthenticationSession' is assigned, but never used
FinancialConnectionsLite.swift:41 warning: Assign-only property 'activeInstance' is assigned, but never used

Please remove the dead code before merging.

If this is intentional, you can bypass this check by adding the label skip dead code check to this PR.

ℹ️ If this comment appears to be left in error, double check that the flagged code is actually used and/or make sure your branch is up-to-date with master.

[find-dead-code]