SDFG.save() now performs tilde expansion. (#1578)

I noticed that it would be cool if I could write
`sdfg.save("~/tmp/faulty.sdfg")` and it would save it into my home
directory, instead in a directory `./~` in some random directory.

dace/sdfg/sdfg.py

@@ -1520,6 +1520,8 @@ def save(self, filename: str, use_pickle=False, hash=None, exception=None, compr
             :param compress: If True, uses gzip to compress the file upon saving.
             :return: The hash of the SDFG, or None if failed/not requested.
         """
+        filename = os.path.expanduser(filename)
+
         if compress:
             fileopen = lambda file, mode: gzip.open(file, mode + 't')
         else: