The Stability of the Layout Support in Core 6.3

There are a few small enhancements that are going to be going into core for 6.3. One of the things that I actually just merged this PR earlier, which is to stabilize the layout support. The layout was one of those experimental API's that have been in core for a while and they're actually being used in production by a few plugins. So it kind of becomes absurd at that point to still have the API marked experimental.