fix: support Terraform AWS Provider v6 (#4646)

Fixes
#4625

Requirements for this PR:
- support Terraform AWS Provider v6
- continue to support Terraform AWS Provider v5 for as long as practical
- avoid the need for another issue to be raised when v7 is eventually
released

This PR therefore includes the following:

- replace current constraints in versions.tf ~> 5.0, ~> 5.27, ~> 5.77 in
the module and submodules with >=5.0, >=5.27, >=5.77
- this follows similar practice adopted by many other popular AWS
Terraform modules, e.g. the [AWS
VPC](https://github.com/terraform-aws-modules/terraform-aws-vpc)
- in the examples, upgrade versions.tf to ">=6.0" except for the base,
multi-runner and permission-boundary examples where it's left as is,
with a comment `ensure backwards compatibility with v5.x`
- ran `terraform init --upgrade` to upgrade `terraform.lock.hcl` files
in examples

Author: paulschwarzenberger

examples/base/.terraform.lock.hcl

@@ -2,7 +2,7 @@ terraform {
   required_providers {
     aws = {
       source  = "hashicorp/aws"
-      version = "~> 5.27"
+      version = ">= 5.27" # ensure backwards compatibility with v5.x
     }
   }
   required_version = ">= 1"

examples/base/versions.tf

@@ -2,7 +2,7 @@ terraform {
   required_providers {
     aws = {
       source  = "hashicorp/aws"
-      version = "~> 5.27"
+      version = ">= 6.0"
     }
     local = {
       source  = "hashicorp/local"