We want to enable a mode that prevent the pills the wrap on multiple
lines in order to control any height overflowing. In monoline mode the
selected items are displayed as text to allow text ellipsis, and the
menu renders the list items with checkboxes.
Adding this new variant makes necessary to reorganize the files to keep
a clear separations of concerns. As of now Select/index.tsx is just an
entrypoint to render either the mono or multi variant of the select.
