[Enhancement][Form] Allow binding Field to nested properties

[kdikov82]

Currently, if a Field is set to a nested property (user.name for example), the setter of the Form will handle this as a string and will not try to set an inner property.

The expected result would be "user:{name: value}" instead of "user.name: value".

A temporary workaround is to modify the onChange of the Field component to return the complex object with added nested property: https://stackblitz.com/edit/bqbxnr-fppiza?file=src%2FFormMultiSelectField.vue,src%2Fmain.vue