Add single instance execution control

[yaythomas]

Context

Implement execution queue mechanism in executor

Technical Requirements

• Implement execution queue mechanism in executor
• Add execution state tracking to prevent concurrent lambda invocations
• Implement queuing logic for multiple execution requests
• Add proper cleanup when executions complete

Acceptance Criteria

• Execution queue mechanism implemented in executor
• Execution state tracking added to prevent concurrent lambda invocations
• Queuing logic implemented for multiple execution requests
• Proper cleanup added when executions complete