Add labels to settings fields (#18072)

...admin/settings/components/SettingHeader/SettingHeader.jsx

...ettings/components/SettingHeader/SettingHeader.styled.jsx

...metabase/admin/settings/components/SettingHeader/index.js

...rc/metabase/admin/settings/components/SettingsSetting.jsx

...tabase/admin/settings/components/widgets/SettingInput.jsx

frontend/src/metabase/admin/settings/utils.js

...d/test/metabase/scenarios/admin/settings/email.cy.spec.js

...est/metabase/scenarios/admin/settings/settings.cy.spec.js

...test/metabase/scenarios/admin/settings/sso/jwt.cy.spec.js

...est/metabase/scenarios/admin/settings/sso/ldap.cy.spec.js

...t/metabase/scenarios/admin/settings/whitelabel.cy.spec.js