`XmpFile::close` can trigger UB

Affected versions of the crate failed to catch C++ exceptions raised within the XmpFile::close function. If such an exception occured, it would trigger undefined behavior, typically a process abort.

This is best demonstrated in issue #230, where a race condition causes the close call to fail due to file I/O errors.

This was fixed in PR #232 (released as crate version 1.9.0), which now safely handles the exception.

For backward compatibility, the existing API ignores the error. A new API XmpFile::try_close was added to allow callers to receive and process the error result.

Users of all prior versions of xmp_toolkit are encouraged to update to version 1.9.0 to avoid undefined behavior.