Rework FileUtil.extractZip() to expose error messages

[str4d]

Currently, FileUtil.extractZip() prints errors to System.out or System.err. This doesn't go anywhere on older Android devices, so we can't capture its output. That doesn't matter for FileUtil itself, but Reseeder uses it to extract reseed files, meaning that in e.g. #1941 we can't tell why it is failing.

We should rework FileUtil.extractZip() to either throw errors (and have the caller catch and then log or print as desired), or use the log system (and have that print to stdout or stderr when invoked via the FileUtil CLI).