codespell: Add CI job fixing spelling issues and fix them

[mjtrangoni]

What this PR does / why we need it:

Trivial PR, add a spelling check with codespell, and fix all findings.

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] DCO signed
• [ ] Chart Version bumped
• [ ] Variables are documented in the README.md