Ensure that re-invocations are time/count limited

[rjlohan]

Currently, although CloudFormation will eventually timeout on waiting for a resource provisioning action, there is no constraint on the duration or number of re-invocations that can be scheduled, leading to essentially unbounded Lambda compute.

Wrapper should auto-inject a net runtime into the callback context and use this to compute a restriction and eventual timeout at https://github.com/aws-cloudformation/aws-cloudformation-rpdk-java-plugin/blob/master/src/main/java/com/aws/cfn/LambdaWrapper.java#L262

This timeout should probably be slightly less than the CloudFormation timeout to ensure that stack events reflect actual progress and termination of handler occurs before CloudFormation abandons the request.

[rjlohan]

Related to #15 which lists additional requirements.

[rjlohan]

Partially implemented with #112