Move `java/preprocessor` to Gradle #95

Job	Run time
Test Processing	1m 29s
(linux/aarch64) Create Processing Build	9m 31s
(linux/x64) Create Processing Build	8m 23s
(windows/x64) Create Processing Build	12m 15s
(macos/x64) Create Processing Build	11m 6s
(macos/aarch64) Create Processing Build	3m 44s
	46m 28s

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