Add the Flipper::Middleware::Memoizer middleware
What does this MR do?
Add the Flipper::Middleware::Memoizer middleware
This ensures we make maximum one call per feature per request.
See
https://github.com/jnunemaker/flipper/blob/v0.10.2/docs/Optimization.md#memoizing-middleware
What are the relevant issue numbers?
Closes #33940 (closed)