☂️ Enhance Etcd spec to include snapshot compaction spec

[shreyas-s-rao]

Feature (What you would like to be added):
Enhance Etcd spec to include snapshot compaction spec, with fields such as resource requests/limits, thresholds/triggers, job spec fields such as TTL, cleanup logic, etc.

Motivation (Why is this needed?):
It would be beneficial to have a fully configurable compaction job spec for every Etcd resource, so that compaction jobs can be configured per etcd resource at a fine-grained level, rather than at the druid-level.

Approach/Hint to the implement solution (optional):

• #502
• #556
• #707

[unmarshall]

@shreyas-s-rao we already have CompactionResources as part of the Backup spec. This is also used in the compaction reconciler. See here. This should also address the remaining task in #707, right?