New Memcached caching module

Create a new integration `MemcachedIntegration`.

First check the Go OTEL memcache instrumentation (https://pkg.go.dev/go.opentelemetry.io/contrib/instrumentation/github.com/bradfitz/gomemcache/memcache/otelmemcache) to see what data Otel is collecting.

Part of https://github.com/getsentry/sentry-python/issues/2949

It should be similar as the `RedisIntegration` but as the first iteration only create cache spans as described here: https://github.com/getsentry/sentry-python/issues/2965

The integration should be auto enabling and patch [pymemcache](https://pypi.org/project/pymemcache/ ).

(There is another lib that is still famous, but it is in maintenance mode and basically going to die: [python-memcached](https://pypi.org/project/python-memcached/) We will not support this lib.)

Bonus:
- [ ] Load test the cache spans generation and publish results somewhere to be confident that this will not add to much overhead.