Optimize nested lambda ClosureInfo memory footprint

[dadhi]

Currently, struct ClosureInfo is the field of the class NestedLambdaInfo, so it is allocated on heap even for a single nested lambda.
Other thing is that it probably may be specialized (some fields removed) for the nested lambda, comparing to the entry point lambda.
Other-other thing is that we may not need it at all for some simple lambdas, e.g. #329

[dadhi]

too complex to optimize