private List<FSCacheInfo> getUnusedFSes() {
		List<FSCacheInfo> results = new ArrayList<>();
		for (Entry<FSRLRoot, FSCacheInfo> entry : filesystems.entrySet()) {
			FSCacheInfo fsci = entry.getValue();
			FileSystemRefManager refManager = fsci.ref.getFilesystem().getRefManager();
			if (refManager.canClose(fsci.ref)) {
				results.add(fsci);
			}
		}
		return results;
	}
Performs maintainence on the filesystem cache, closing() any filesystems
that are not used anymore.
Ghidra/Features/Base/src/main/java/ghidra/formats/gfilesystem/FileSystemInstanceManager.java