Use default_tags in AWS Provider statements

[dms1981]

As a possible example for ministryofjustice/modernisation-platform#1519, this PR implements the use of default_tags as configured in version 5.0 and above of the Terraform AWS Provider, using the common values in local.tags:

provider "aws" {
  default_tags { tags = local.tags }
}

[github-actions]

TFSEC Scan Success

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</details> #### `Checkov Scan` Success
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CTFLint Scan Success

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Setting default tflint config...
Running tflint --init...
Installing "terraform" plugin...
Installed "terraform" (source: github.com/terraform-linters/tflint-ruleset-terraform, version: 0.5.0)
tflint will check the following folders:

Trivy Scan

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[SteveLinden]

We may have tried this before but if it works we'll save some time/effort in future