Circular import of NcCheckboxRadioSwitch and NcCheckboxContent

[raimund-schluessler]

After #4663 NcCheckboxRadioSwitch and NcCheckboxContent each import from each other. While this doesn't seem to be an issue for the vue 2 builds, it is the reason why the styleguide currently does not work in #4688.

I would propose to move these lines

nextcloud-vue/src/components/NcCheckboxRadioSwitch/NcCheckboxRadioSwitch.vue

Lines 310 to 313 in 0a3e598

	export const TYPE_CHECKBOX = 'checkbox'
	export const TYPE_RADIO = 'radio'
	export const TYPE_SWITCH = 'switch'
	export const TYPE_BUTTON = 'button'

into NcCheckboxContent and import the types from there.