This change fixes an exception,
when Skiko is loaded multiple times
in a multi-classloader environment on Windows:

java.lang.RuntimeException: Can't wrap nullptr
	at org.jetbrains.skija.impl.Native.<init>(Native.java:13)
	at org.jetbrains.skija.impl.Managed.<init>(Managed.java:15)
	at org.jetbrains.skija.impl.Managed.<init>(Managed.java:11)
	at org.jetbrains.skija.paragraph.ParagraphBuilder.<init>(ParagraphBuilder.java:15)

The exception was happening, because
when `skiko.library.path` is not set,
icudtl.dat was copied into cacheDir,
even if the library was copied into copyDir.

Also icudtl.dat was always copied to `java.io.tmpdir`,
and a different version was not overwritten.