Multi Input/Multi Combo improvements

[droshev]

Other tasks may pop alone the way.

• [x] merge platform InputGroup(all artifacts) to core (+)
• [ ] move platform Form Container(all artifacts) to come
• [ ] adopt Form Field Errors in core form components(input, select, dropdown, radio, checkbox, textarea, switch, input group) and maybe multi input/compo as a separate task
• [ ] deprecate platform multi combo/multi input
• [ ] compare core and platform APIs and bring all the API into core components
• [ ] keep a11y implementations
• [ ] refactor and optimize the core components, delegate the platform impl to core
• [x] check issue https://github.com/SAP/fundamental-ngx/issues/10958
• [x] check my last comment from this issue https://github.com/SAP/fundamental-ngx/issues/10998
• [x] check this issue https://github.com/SAP/fundamental-ngx/issues/11025 (+)

[droshev]

[droshev]

@N1XUS Can you check this one? thanks

[droshev]

We will revisit the component once we bring the accessibility specs