Fix Checkov Scan findings.

[kunduso]

CKV2_AWS_64: Ensure KMS key Policy is defined for resource "aws_kms_key" "encryption_rest" {}
CKV_AWS_173: Check encryption settings for Lambda environmental variable for resource "aws_lambda_function" "lambda_run" {}
CKV_AWS_115: Ensure that AWS Lambda function is configured for function-level concurrent execution limit for resource "aws_lambda_function" "lambda_run" {}
CKV_AWS_116: Ensure that AWS Lambda function is configured for a Dead Letter Queue(DLQ) for resource "aws_lambda_function" "lambda_run" {}