L2 ElastiCache support

[dbartholomae]

Description

Adding a first L2 construct for ElastiCache ReplicationGroups which will take care of SubnetGroups as well.

Roles

Role	User
Proposed by	@dbartholomae
Author(s)	@dbartholomae
API Bar Raiser	@corymhall
Stakeholders	not yet decided

See RFC Process for details

Workflow

• [x] Tracking issue created (label: status/proposed)
• [x] API bar raiser assigned (ping us at #aws-cdk-rfcs if needed)
• [x] Kick off meeting
• [ ] RFC pull request submitted (label: status/review)
• [ ] Community reach out (via Slack and/or Twitter)
• [ ] API signed-off (label api-approved applied to pull request)
• [ ] Final comments period (label: status/final-comments-period)
• [ ] Approved and merged (label: status/approved)
• [ ] Execution plan submitted (label: status/planning)
• [ ] Plan approved and merged (label: status/implementing)
• [ ] Implementation complete (label: status/done)

---

Author is responsible to progress the RFC according to this checklist, and apply the relevant labels to this issue so that the RFC table in README gets updated.

[dbartholomae]

Added @corymhall as API bar raiser

[dbartholomae]

@corymhall Sooo - if I understand correctly, the next step is an execution plan? Or can I just go at implementing parts and create a PR for the aws cdk repo? We didn't actually add all the labels that are shown in the first comment in this thread in the check list, so if I need to add some of those, please let me know as well.

[corymhall]

@dbartholomae we can move right into implementing.

[awsmjs]

Closing this ticket. We believe the functionality is beneficial, but does not intersect with the core framework and should be vended and maintained separately.