use feature based caches and update metrics

[wagpa]

Changes

• replace closure-type metrics capture with custom macro #[metrics(...)]
• add additional metrics
• fixate cache structure to two cache levels (local and remote)
• add additional docker image for Redis cache

Breaking Changes

• move Redis remote cache behind build feature
• disable Redis remote cache by default (affects default image)

To continue using Xenos with Redis as remote cache, the Redis docker image has to be used. These changes were made to (1) improve the readability of the code (in respect to the metrics) and (2) to ensure that future caches do not conflict with their dependencies or bloat up the binary.

[scrayos]

Okay, I've reviewed everything and looks nice! We can look into the github workflow changes together.