ux: new style for `SplitButton` #4294

Job	Run time
Prepare version string	5s
Build / Build Windows x64	3m 21s
Build / Build macOS (Apple Silicon)	3m 6s
Build / Build Windows ARM64	3m 40s
Build / Build Linux (arm64)	4m 10s
Build / Build macOS (Intel)	3m 1s
Build / Build Linux	3m 2s
Package / Package Linux (linux-arm64)	1m 0s
Package / Package Windows (win-arm64)	30s
Package / Package Windows (win-x64)	26s
Package / Package macOS (osx-arm64)	20s
Package / Package Linux (linux-x64)	55s
Package / Package macOS (osx-x64)	17s
	23m 53s

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