VED-1044: Create Cloudwatch Dashboard with Parameterised Terraform (#1226)

* Set up imms-metrics-dashboard-dev with json file

* Add condition to not re-deploy dashboard upon a PR

* Generate alarms based on env

* Parameterise DynamoDB Reads and Kinesis

* Tidy up dynamodb metrics and parameterise Kinesis and SQS

* Organise terraform file to match layout of dashboard

* Set up lambdas grouped by area and update widget positioning

* Add lambda metrics for API, batch and Ancillary

* Self review

* Fixes from terraform plan

* Add ElastiCache CPUUtilization

* Fix widget positioning

* Update alarms widget height

* Add Redis lambdas to dev

* Address review comments: Refactor sub environment vars, add comments, typos

* Review comment. Remove duplicate queue metric for non dev environments

Author: edhall-nhs