[Infra]: Upgrade Terraform core, providers, and module versions

[TylerHendrickson]

Why is this issue important?

For reasons related to security and stability, we want to stay up-to-date with our dependencies. Upgrading our Terraform code to be compatible with the latest version of Terraform (currently 1.6.6) unlock viable upgrade paths for certain modules and provider features that we rely upon in this project.

Current State

• Terraform is outdated, currently at 1.3.6 (current latest available is 1.6.6).
• Our AWS provider version is outdated, currently at 4.67.0 (current latest available is 5.31.0)

Certain module upgrades are not compatible with our current versions, for example:

• terraform-aws-modules/rds-aurora/aws Chore [deps:terraform]: Bump terraform-aws-modules/rds-aurora/aws from 8.5.0 to 9.2.0 in /terraform/modules/gost_postgres #2711
• terraform-aws-modules/cloudfront/aws Chore [deps:terraform]: Bump terraform-aws-modules/cloudfront/aws from 3.2.2 to 3.3.1 in /terraform/modules/gost_website #2712

Expected State

• Terraform core version is at least 1.6.6
• AWS provider version is at least 5.31.0
• The terraform-aws-modules/rds-aurora/aws module version is at least 9.0.0
• The cloudposse/waf/aws module version is at least 1.3.0

Implementation Plan

1. In a local development environment, manually bump version constraints defined in terraform/main.tf as well as terraform/.terraform-version.
2. Attempt to initialize Terraform with terraform init -backend=false. Observe what breaks and attempt to fix the problems directly, or create issues for follow-up.
3. After fixing issues preventing successful Terraform initialization with newer core and AWS provider versions, determine upgrade viability for third-party modules listed above (worth spot-checking for any others).

Relevant Code Snippets

No response