rule: Lambda default memory and timeout rules

[nmoutschen]

Key information

• Rule issue: rule: Lambda default memory settings #47 rule: Lambda default timeout #48
• cfn-lint rule ID: ES1005 and ES1006
• tflint rule name: aws_lambda_function_default_memory and aws_lambda_function_default_timeout

Summary

Add checks for default memory size and timeout for Lambda functions.

Checklist

• cfn-lint: add rule
• cfn-lint: add import in rules/__init__.py
• cfn-lint: add test templates
• tflint: add rule
• tflint: add tests
• tflint: add in rules/provider.go
• docs: add new section in documentation
• docs: add reference in rules/index.md