Explore potential CLDR locale data byte savings by omitting trailing undefined values #42315
Description
As noted by @petebacondarwin in #42230 (comment). Mostly for tracking
In the CLDR locale data we often output data as followed: [a, b, undefined, undefined]. This is basically the same as [a, b] - as long as we don't care about the length of the array.
We might be able to further improve this by trimming any trailing undefined values from the locale array.
It's unclear whether this could land in a minor/patch, or whether we should wait for a major. If experiments show that we can do this optimization, then we could figure out where to land it. I assume a major is more suitable in case users rely on the locale data length (for unknown reasons?)