☂️ 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):

• [Feature] Support configurable etcd-events-threshold per etcd object #502
• [Feature] Enable automatic cleanup of finished compaction jobs and make TTL configurable #556
• [Feature] Configurable resource requests/limits for compaction jobs #707