without this, ids get silently ignored for =react

    ManageIQ.component.addReact('Foo', Foo); // works
    ManageIQ.component.addReact('Foo', Bar); // throws
    ManageIQ.component.addReact('Foo', Baz, { override: true }); // works

previously, the third param was an array of instances,
now it's an options object, with instances an optional key

and attempting to add a numeric name, or a component twice without override throws

switch from Map<{name, blueprint}, Set<instances>>
to {name: {name, blueprint, instances: Set}}

That way, we ensure a component is only registered once under a name.

And removed the surprising "instance.id must be a string" logic.

needed for now, later fixing in css