[Visual] Compute bounding box in VisualMesh

[alxbilger]

---

By submitting this pull request, I acknowledge that
I have read, understand, and agree SOFA Developer Certificate of Origin (DCO).

---

Reviewers will merge this pull-request only if

• it builds with SUCCESS for all platforms on the CI.
• it does not generate new warnings.
• it does not generate new unit test failures.
• it does not generate new scene test failures.
• it does not break API compatibility.
• it is more than 1 week old (or has fast-merge label).

[fredroy]

And should computeBBox() compute BBox if:

• computeOnlyVisible is true (meaning computeBBox was called for rendering)
• vparams->displayFlags().getShowVisualModels() is false ?

?