Replace fifocache with embedded-cache configuration

Currently all our LokiStack sizes are using the fifocache config block to use fixed 500MB in-memory caching indices/chunks/results. The configuration was replaced by a more easy to use block called embedded-cache that allows controlling the size and TTL. This yields that our pods are throwing some deprecation notices, e.g.:

caller=cache.go:114 msg="fifocache config is deprecated. use embedded-cache instead"
caller=experimental.go:20 msg="experimental feature in use" feature="In-memory (FIFO) cache - embedded-cache"
caller=cache.go:114 msg="fifocache config is deprecated. use embedded-cache instead"
caller=experimental.go:20 msg="experimental feature in use" feature="In-memory (FIFO) cache - chunksembedded-cache"
 

Acceptance Criteria

• Replace the config block with using the old fifocache defaults for size and TTL.
• Deprecation notices are not showing up in any Loki pod.

Developer Notes:

• Configuration options: https://grafana.com/docs/loki/latest/configuration/#cache_config