bugfix in global_benchmark.py

[quaquel]

This PR moves the sys.insert statement to be before any mesa imports. The old version resulted in potentially importing the examples from the installed version of mesa.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
BoltzmannWealth	small	🔵 +1.1% [+0.6%, +1.5%]	🔵 +1.2% [+1.0%, +1.4%]
BoltzmannWealth	large	🔵 -0.0% [-0.6%, +0.5%]	🔵 -0.3% [-0.6%, +0.0%]
Schelling	small	🔵 +1.2% [+0.9%, +1.5%]	🔵 +0.6% [+0.4%, +0.8%]
Schelling	large	🔵 +0.1% [-0.7%, +0.7%]	🔵 +0.7% [-0.4%, +2.2%]
WolfSheep	small	🔵 +0.6% [+0.3%, +0.9%]	🔵 +0.5% [+0.4%, +0.7%]
WolfSheep	large	🔵 -0.1% [-0.6%, +0.5%]	🔵 +1.3% [-0.2%, +3.3%]
BoidFlockers	small	🔵 -1.5% [-1.9%, -1.1%]	🔵 +0.5% [-0.0%, +1.0%]
BoidFlockers	large	🔵 -0.9% [-1.7%, +0.2%]	🔵 +0.3% [-0.6%, +1.2%]