MNT: Expand exception preservation to more scenarios

[pauldmccarthy]

Use the mechanism from #152 in more scenarios, including:

• at creation
• seek
• build_full_index
• export_index
• import_index

Also:

• fixes a subtle bug in zran_file_util.c:_fwrite_python, where an exception raised by the file-like write method could be absorbed.
• Attempt to work around unexplainable test failures on Windows+free-threaded Python
• Remove a workaround for cython<=0.26, where a cdef method could not be decorated with contextlib.contextmanager