Executor with subpatterns

[krishnangovindraj]

Release notes: product changes

Prepares the PatternExecutor for functions with the ability to recurse into nested patterns.

Motivation

Making nested patterns transparent to the executor should allow a cleaner implementation of the cycle-detection & retry logic for recursive functions.

Implementation

• New PatternExecutor implementation
• Ports the negation executor to the new NestedPatternExecutor pattern.