feat: Support cloudwatch_log_group_tags parameter

[take-five]

Description

Add support for configuring tags for CloudWatch log groups only via cloudwatch_log_group_tags variable.

Motivation and Context

Similar to db_parameter_group_tags, sometimes it is necessary to configure additional tags on CloudWatch log groups only. For example, in our organization we want to mark CloudWatch log groups with RDS logs as sensitive via a tag, but we don't want to apply this tag to all resources created by this module.

Breaking Changes

No

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects

I ran terraform plan from "examples/complete-postgres" folder and checked that aws_cloudwatch_log_group resources include a custom tag:

  # module.db.module.db_instance.aws_cloudwatch_log_group.this["postgresql"] will be created
  + resource "aws_cloudwatch_log_group" "this" {
      + arn               = (known after apply)
      + id                = (known after apply)
      + log_group_class   = (known after apply)
      + name              = "/aws/rds/instance/complete-postgresql/postgresql"
      + name_prefix       = (known after apply)
      + retention_in_days = 7
      + skip_destroy      = false
      + tags              = {
          + "Example"    = "complete-postgresql"
          + "Name"       = "complete-postgresql"
          + "Repository" = "https://github.com/terraform-aws-modules/terraform-aws-rds"
          + "Sensitive"  = "high"
        }
      + tags_all          = {
          + "Example"    = "complete-postgresql"
          + "Name"       = "complete-postgresql"
          + "Repository" = "https://github.com/terraform-aws-modules/terraform-aws-rds"
          + "Sensitive"  = "high"
        }
    }

• I have executed pre-commit run -a on my pull request

[antonbabenko]

This PR is included in version 6.10.0 🎉

[github-actions]

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