Add skip-schema-validation flag

[JvD-Ericsson]

What this PR does / why we need it: Adds a "--skip-schema-validation" flag option for helm install, upgrade, lint, and template that skips validation of the values.schema.json file.

closes https://github.com/helm/helm/issues/10398

Special notes for your reviewer: This is my first time contributing, so please let me know if there is something I am doing wrong : )

If applicable:

• [ ] this PR contains documentation
• [ ] this PR contains unit tests
• [ ] this PR has been tested for backwards compatibility

Signed-off-by: Jeff van Dam [email protected]