Initial feature gating and A/B testing integration (#3122)

* Add statsig dependency

* Add SDK provider

* Move to separate file, add tier and hashing

* Disable local storage for now

* Add initial gate testing fixture

* Fork for web just in case

* More WIP

* wip

* Rm test gate

* Add shim on native

* Clarify

src/lib/statsig/statsig.tsx

@@ -0,0 +1,11 @@
+import React from 'react'
+
+export function useGate(_gateName: string) {
+  // Not enabled for native yet.
+  return false
+}
+
+export function Provider({children}: {children: React.ReactNode}) {
+  // Not enabled for native yet.
+  return children
+}