Ability to run multiple prompts/MCPs in the background (/async)

Implementation of a new /async parameter.

1. Parameter Functionality:
- Accept a list of prompts and MCPs to be executed asynchronously
- Format: /async=[prompt1,prompt2,MCP1,MCP2]
- Potentially, define an order where the same number indicates that they need to be executed together and wait for both to finish

2. Execution Process:
- System identifies items marked for async execution
- Launches parallel processing of specified prompts and MCPs
- Maintains execution order where necessary
- Manages resource allocation for parallel operations

3. Output Handling:
- Results from async executions saved to designated output file
- File format should include:
- Execution timestamp
- Input identifier (prompt/MCP name)
- Execution status
- Tokens used
- Result data: JSON or structured format for easy parsing