experimental init: Fix Solara import by making it lazy

[EwoutH]

In the experimental __init__.py, it always tries to import the "old" solara_viz module, even if it's not needed because only the cell space is used. This PR wraps that in a try block to also allow using the experimental cell space without Solara installed.

Quick and dirty fix for #2343, follow up after #2265, unblocks projectmesa/mesa-examples#198.

[github-actions]

Performance benchmarks:

Model	Size	Init time [95% CI]	Run time [95% CI]
BoltzmannWealth	small	🔵 +0.8% [+0.0%, +1.6%]	🔵 +1.3% [+1.1%, +1.4%]
BoltzmannWealth	large	🔵 -0.7% [-2.2%, +0.8%]	🔵 +1.0% [-0.2%, +2.1%]
Schelling	small	🔵 -0.4% [-1.0%, +0.2%]	🔵 +0.1% [-0.4%, +0.7%]
Schelling	large	🔵 -0.9% [-2.2%, +0.5%]	🟢 -6.4% [-8.8%, -4.4%]
WolfSheep	small	🔵 -0.8% [-1.3%, -0.4%]	🔵 +0.5% [+0.1%, +1.0%]
WolfSheep	large	🔵 -0.3% [-1.3%, +0.8%]	🔵 +1.3% [-1.7%, +4.8%]
BoidFlockers	small	🔵 +0.6% [-0.1%, +1.3%]	🔵 +1.5% [+0.7%, +2.2%]
BoidFlockers	large	🔵 +1.6% [+0.5%, +2.6%]	🔵 +1.2% [+0.8%, +1.7%]