Take jwksResolverExtraRootCA out of TechPreview

Several customers are using the `jwksResolverExtraRootCA` parameter that currently is in TechPreview, and need it to be a supported feature for their production environments, thus they request that it's taken out of TechPreview and become a supported feature. 

Acceptance Criteria:

• Create new field in SMCP that allows users to configure a cert, in PEM format that can be used to validate the serving cert of a JWKS server
• Verify that charts are rendered correctly and that the cert is configured correctly for use by pilot/istiod