Previously we had been using the “…UI” suffix on React components which were styled using the CSS-in-JS emotion package, particularly when those components’ names would clash with the unstyled versions. However, this was never documented and is unclear and inconsistently applied. Moreover, those components were never meant to be part of a public API.
In this PR, we rename all such components to remove that suffix. Mostly this is inside the @automattic/composite-checkout package, but also in calypso and in the editing-toolkit app (see #44821).