Expand "lv_btnmatrix_set_one_check" to allow radio-button functionality

Right now there is no radio button in lvgl.

It seems like there almost exists this functionality in the btnmatrix widget, when combined with the lv_btnmatrix_set_one_check function.

The only thing missing is that lv_btnmatrix_set_one_check makes it so only one thing can be checked, but it doesn’t make is to that one thing must be checked. With a radio button, one of the options must be selected.

It sounds quite reasonable. I can’t imagine a use case where either 0 or 1 option can to be selected. It should be always 1. So I’d agree to update lv_btnmatrix_set_one_check to ensure there is at least one checked button.