Update LambdaDeployemnt with simpler logGroup configuration

[zmillman]

logGroup is a recently available configuration that makes it easier to manage where logs are sent from lambdas (https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_lambda.Function.html#loggroup)

Instead of keeping the function name static, we can use a static logGroupName to get the same benefits.