Flow input validation in the UI

[loicmathieu]

Feature description

Input validation was done in the backend thanks to #1123.

Those validations are included in the Flow JsonSchema, they must then be displayed on the Flow input form when executing a flow. Each input that have validation must have the validation shown somewhere in the form.

We may also validate on the UI to avoid sending wrong input to the backend, but be aware that if we do that, validation will be duplicated on the UI and the backend with a risk of having divergent validation later if things evolve not together.

[Skraye]

Done in #1234