[v12] feat(ui-form-field): rework FormFieldGroup

[ToMESSKa]

INSTUI-4871

ISSUE:

• the remaining of tokens in FormFieldGroup needs to be removed because they are now longer needed for newError-style errors
• FormFieldMessages theme.ts needs to be removed

TEST PLAN:

• test FormField, FormFieldGroup, CheckBoxGroup, RadioInputGroup and DateTimeInput examples with errors, there should be no visual change from the current v12

[github-actions[bot]]

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