Log execution time of scene rendering in the Manim Checkhealth command

[chopan050]

Easy review! Requested by @uwezi to see how much time a helpee's computer takes to render the example scene, to evaluate whether a particular scene is actually slow/unoptimized or it's just the computer.

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested

[behackl]

LGTM, tested and works.

[JasonGrace2282]

Do you mind using timeit.timeit? It's better for benchmarking because it prevents the garbage collector from scheduling a run at a bad time.

[JasonGrace2282]

Works for me, thanks :)