fix: Pass the OpenAI API Key to Crew()

[erichare]

This pull requests sets the OpenAI API Key as an environment variable and adds a new input to provide it in the hierarchical crew component

[codspeed-hq]

CodSpeed Performance Report

Merging #4555 will degrade performances by 16.47%

_{Comparing bugfix-crewai-api-key (33b12eb) with main (01431ee)}

Summary

⚡ 2 improvements
❌ 1 regressions
✅ 12 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	bugfix-crewai-api-key	Change
⚡	test_successful_run_with_input_type_text	454.8 ms	379 ms	+20.02%
⚡	test_successful_run_with_output_type_any	455.9 ms	347.3 ms	+31.29%
❌	test_successful_run_with_output_type_debug	444.3 ms	531.9 ms	-16.47%