[#192] Update variables to use static values or locales when appropriate

[malparty]

• Close #192

What happened 👀

Move default variables not used elsewhere to direct values or locals.

Only remove variable when ALL environments (e.g. Production and Staging) need to have the same values:

• ALB stickiness
• Cloud watch logs retentions
• ECS scale_in/out_cooldown_period
• RDS engine, port, logs
• VPC configs

Insight 📝

Some variables are kept with a purpose in mind:

Variable	Purpose
rds.autoscaling_min/max_capacity	PROD might need higher capacity than staging
bastillon.*	Staging can have lower costs with a smaller instance and capacity.

Proof Of Work 📹

No feature changed. Tests are passing.