Reduce AWS costs from Herd-MDL development

[nateiam]

As Herd PO I want to reduce AWS costs without making functional compromise

Later we might need to take additional cost-saving steps but initially let's see what we can do without compromising anything.

Acceptance Criteria

• Time-box analysis has been performed to identify low-hanging fruit cost savings opportunities
• Cost per stack is reduced by >= 25%
• Cost per hour per stack is reduced by >= 25%

Technical notes:

• Eliminate RDS snapshot when RDS is created and prior to RDS deletion
• Remove RDS snapshots from all previous Herd-MDL stacks
• Reduce instance size for EC2, RDS, and EMR -- but ensure MDLT still works and there is some room to scale the environment for POC or lightweight operations

[sbalkee]

1. Cost analysis EC2, RDS, EMR
2. Change Templates to use new instance types
3. Analyze RDS snapshot cost and options
4. Implement RDS snapshot options