Allow DataSize to be initialized at build time

Previously, Graal failed to build a native image as DataSize was
unintentionally initialized at build time. This commit workarounds the
faulty assumption by flagging it as safe to initialize at build-time.

Closes gh-28328

spring-core/src/main/resources/META-INF/native-image/org.springframework/spring-core/native-image.properties

@@ -1 +1,2 @@
-Args = --initialize-at-build-time=org.springframework.core.NativeDetector
+Args = --initialize-at-build-time=org.springframework.core.NativeDetector \
+--initialize-at-build-time=org.springframework.util.unit.DataSize