fix: Use local log_group throughout, fixing log configuration with Lambda@Edge.

[theherk]

Fixes #650 and #665.

Description

Motivation and Context

This allows module implementations using lambda_at_edge = true to actually log to Cloudwatch.

Breaking Changes

This will cause changes for users using lambda_at_edge = true, but is is a fixing change.

How Has This Been Tested?

• I have verified the changes in my infrastructure.

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

  terraform-aws-lambda
ᐅ pre-commit run -a
Terraform fmt............................................................Passed
Terraform wrapper with for_each in module................................Passed
Terraform docs...........................................................Passed
Terraform validate with tflint...........................................Passed
Terraform validate.......................................................Passed
check for merge conflicts................................................Passed
fix end of files.........................................................Passed
trim trailing whitespace.................................................Passed
mixed line ending........................................................Passed