form.Container: setValues() => no support for nested structures

This bug sneaked into the framework when adding the setConfigs() method.

The current logic:

    async setValues(values={}, suspendEvents=false) {
        Object.entries(values).forEach(([key, value]) => {
            values[key] = {value}
        })

        await this.setConfigs(values, suspendEvents)
    }

is fine for simple forms, but not sufficient for nested structures.

All top level (root) items will get prefixed with value. However, we want to do this for all leave items instead.

This one will need testing!

@subramaniyamP: thanks for the heads up!

FYI: @dztoprak @Dinkh